This'll duplicate some above material, but going with how my group adjudicates and/or the logic behind it all:
1) There are no 'monster knowledge' skills...
Sorta. Rather than a fixed table like 3rd/Pathfinder, it's organic, letting each group tailor it to their own playstyles. But there is monster knowledge: the Ranger has "advantage" on Intelligence checks to recall information about "favored enemies;" the Battlemaster can study an enemy and learn details about a foe. It's up to the DM how much or little is given in a knowledge check about a monster. Rather than pausing combat to reference a table, the DM has a lot of leeway to adjudicate this.
D&D is big on not turning the game into Law and Order by searching for a Rule every five minutes.
1. DM could say you only get lore, like whether they travel in packs or what languages they speak. You don't get combat mechanics.
2. The DM could assign the basic DC checks (10/15/20) and on the fly give out something. DC 10 (easy) is common knowledge, like everyone knows a werewolf can only be hurt by silver, or DC 15 (moderate), a werewolf can transmit its disease through its bite only, not its claws, or DC 20 (difficult), a werewolf's disease is a special curse.
3.
What we do:Personally, I don't ever want to slow the game down. I might ask the player if there's any good reason they'd know about ghosts. If all the player says is "I attended my great-aunt's funeral," that's not enough, but if they say "I can cast a necromantic spell and as part of my studies they made me spend time on chapters involving undead. Maybe I picked up something there." Roll it, 10/15/20 Intel check and we'll see. I also follow the optional +5 rule that says if your ability score is 5 or better than the check, you auto succeed. Genius characters will know a lot and it saves time, so long as the player reminds me.
2) There doesn't seem to be much variation in some of the basic builds if you want to be effective...
D&D 5th isn't supposed to be about the "build." I believe there's a Mike Mearls design interview that recently popped up about this. Make an interesting character and it won't matter if you have 3 archers with the same stats. And, after several years of play, there isn't a "right" or "wrong" cleric or wizard. Seriously, people are going to be fine playing anything they want.
Coming from Pathfinder to D&D as well, that's been an adjustment for my players, but we all specifically wanted that.
3) The only book caster is the wizard correct? So all these spellbooks we are finding are basically useless (no wizard in our group). True?
Others answered part #1, but spellbooks are never useless. This should be an opportunity for some roleplay. Maybe the kobold shaman would be willing to grant safe passage if you bribe him with a spellbook. Maybe some apprentice would be willing to steal from his master's potion closet to swap you for that book. Use it as a chance for more roleplay, a side adventure. Don't perceive everything as loot to be equipped or put in the trash pile and hopefully the DM will feed off this creativity.
4) My wife is new to RPG's in general She loved the idea of the ranger's animal companion...
Yeah, it's Rules Action Economy, but disagree the pet sucks. The pet is pretty strong at lower levels, probably stronger in its attack than the character. Let's use the
Wolf at Ranger 3rd level. Our Buffed Wolf has +6 attack, does 2d4+4 damage, has 18 hit points (max), can knock enemies prone, and gets Advantage next to allies. That's a killer superior to your ranger, who likely with a 16 attribute has a +5 attack, does 1d8+3 damage, and maybe has 21 hit points with no special attacks like our wolf. So, your character gets to choose: do I attack or does my Pet attack? (At 3rd level, the Wolf attack rocks). It wouldn't be balanced Action Economy if you found a way to get 2 strong attacks and everyone else has 1 Action. I know it sounds silly, you order your Pet to attack and then it won't keep attacking (unless it's an AoO, which makes even less sense, right?). But the Rules were written for a reason to keep an Action imbalance from happening. Not saying its perfect or that someone couldn't house rule pets that scale better into high levels. Also, note, your Pet will defend you if you go to 0 hit points, and you're the only class that can say that you can still get attacks when incapacitated. So now you know, and knowing is half the battle.
5) If I am reading this correctly, your 2 good saves will go up both with your proficiency bonus and because you will probably increase those stats. But your other 4 saves never increase at all. Really?...
Yep, by design they don't need to. With Bounded Accuracy, the numbers stay within reason. Coming from Pathfinder, this was a jolt, but it works. And, it ensures you're always vulnerable to something. Remember, this works for monsters too. Most don't get any save bonuses at all except their ability scores.
6), 7), 8) nothing to add.