Well first thing I'll second what the previous poster said: be prepared to be outclassed by any other powergamers.
A perfectly min-maxed fighter/wizard is about as effective as a fighter constructed with no concern for min-maxing whatsoever. (Although he's better than a poorly constructed fighter).
#2. You're shooting yourself in the foot by going fighter/sorceror unless you go dragon disciple. (And in that case, you only want one or two levels of sorceror). Fighter/Wizard is a much better combination since you can use the intelligence as an AC bonus for the duelist class and as a prerequisite for expertise. Fighters have very little synergy with charisma. Far more significantly, however, wizards get their spells earlier. If you work with a 1/1 progression, by the time your fighter/sorceror is sixth level he still won't have 2nd level spells. If fighter comes first in the class lineup, the fighter/sorceror will get a single second level spell at 8th level. OTOH, a wizard will get a second level spell at 6th level. If you want the fighter/wizard to be able to cast the spells as many times/day as a sorceror, just specialize and prepare one of your four spells (at each level) in each of your four slots (2 for being an even levelled wizard, one for specialization, one for int bonus). Now you can cast as many spells per day at your highest level as the sorceror and you have more flexibility because you can pick any of your four spells on any particular day. At odd numbered levels, you get an even better deal because you can actually cast spells of one level higher than the sorceror.
#3. Bladesinger is a good class but it's really designed for a fighter/wizard as they have int based progression and bonusses. It's also designed for a character with only one or two wizard levels since it has a seperate spell progression.
#4. How much charisma do you need? It depends. If you want to pack the spellcasting power, you'll need at least a 14 and count on using all your increases for charisma and getting a cloak of charisma ASAP. If you only want a couple levels (up to 5 levels), an 11 or a 12 will suffice.
#5. Suggested progressions:
1. Pal
2. Pal
3. Sor
4. Sor
5. Sor
6. Sor
7-11. Spellsword
12-20. Sacred Exorcist (Defenders of the Faith).
You'll end up with 8th level arcane spells, very good saves, reasonable fighting ability (+13 BAB and feats), no arcane spell failure from your mithril breastplate, and some other nifty abilities.
or for a chaotic character more oriented towards melee
1. Ftr
2. Ftr
3. Sor
4. Sor
5. Ftr
6. Ftr (wp. specialization)
7. Sor
8. Sor
9. Sor
10. Sor (pick haste or blink as your 3rd level spell)
11-20. Holy Liberator
This way you end up with a +17 BAB and the ability to cast 3rd level arcane spells
or
1. Ftr
2. Sor
3. Sor
4. Sor
5. Sor
6. Sor
7-16. Spellsword
17. Sor
18-20. Fighting Prestige class or fighter
This way you'll end up with a +14 BAB and the spellcasting ability of an 11th level sorceror--enough to run a persistent Shield. You'll also be able to run around in mithril full plate with no arcane spell failure.
Either way: some strategies:
1. You won't have as many hit points as a fighter but you can still have a reasonable amount. Make sure your con is at least 14 and select a toad familiar. In the end, you'll have a reasonable number of hit points.
2. You have sor/wizard spells for defense. Use them. You have the potential to have just about the best ACs in the game. Shield should be one of your first spells. Shield, a chain shirt, and a large shield give you a base AC of 23 at first level. Tack on a decent dex bonus and you'll be very difficult to hit. As you progress, add protection from evil, haste, and cat's grace. Blink is very effective as well if you get the expert tactician feat. Bull's strength will help you make up for a strength that will probably be mediocre and the lack of weapon specialization (at least in build #1).
3. Use your feats to enhance your fighting ability. (And to qualify for prestige classes). Your attack bonus will be a weak point for this character. Take weapon focus (that's also a prereq for Holy Liberator). If you're not the party's main stand up front fighter, consider combat reflexes and a reach weapon. If you combine it with spring attack, this will enable you to negate your opponents advantage in number of attacks. (Combined with expert tactician and the blink spell, you will probably end up with three attacks for every attack they make). The only metamagic feats that will really help you are Extend Spell and Persistent Spell (for shield) but they won't do you any good until high level so you can afford to wait.
4. You can live with Arcane Spell failure. Mage Armor doesn't last all day and will use up one of your precious spells known. A mithril chain shirt can be enchanted and is generally better. And it's only got 10% arcane spell failure. Plus, it will stack with a large shield (unlike Mage Armor).
5. You don't need Magic Missile. At least not initially. You'll do more damage casting true strike every other round and then power attacking with a greatsword, glaive, or even a longsword than you will casting a magic missile every round. Plus you can do it for twice as long and you can use true strike as an automatic disarm against humanoid opponents (So I have +24 (more if you've got a bigger weapon than your opponent) on the opposed roll at second level--beat that). Magic Missile won't really be useful for you until you hit 5th level as a sorceror and even then it won't be really really useful until you gain spellsword levels and can channel it through your sword. (True strike in haste action+Power Attack+Enchanted weapon+Weapon Damage+Magic Missile Damage (through spellsword channel) is an effective combo).
6. Keep magic items to enhance your capabilities. A scroll of Magic Weapon will let you hurt damage resistant creatures early on even if you don't have it as a known spell (it's a poor choice as it doesn't scale). Similarly, a scroll of See Invisibility will help you out as you reach mid levels. Scrolls of Haste, protection from arrows, and stoneskin will also be very helpful in terms of your fighting ability. (And none of them will be very hard to successfully cast by the time you can afford them). A wand of Shield could be a boon to you if you decide to wear full-plate and go for non-verbal spells only.
7. With regard to your large shield, don't equip it until you're ready to enter melee combat. When you do, you're done casting spells (for the most part). This will enable you to keep your arcane spell failure to a minimum (if you're not using the shield, you don't suffer arcane spell failure) while still enjoying the defensive bonus of the shield when you enter combat.
8. Only cast short term buffs (shield, protection from evil, haste) when you're pretty sure combat is about to break out. Ones like Haste should be saved for the first round of combat.
9. Cast long term buffs when you think combat may occur in the next hour or so. So cast your bull's strength, cat's grace, protection from arrows, or mage armor (if you decide to use it) when you're entering a dungeon or other dangerous situation.
