At low levels (about 1-4lvl) combat is always dangerous and unpredictable. It can turn its course with one lucky hit or missed save. That said your bad guy is not that dangerous or optimized.
I can't really see how he is going to get any use from Extend spell and Widen spell. Remember that metamagic feats increase the level of the base spell, Widen spell by three levels, so a 2nd lvl glitterdust is suddenly a 5th level spell. The bard will not be able to cast any of his spells altered with the Widen spell feat.
As a Bard his main strengths are good skills and increasing allies’ abilities with songs. As it does not seem that he will be able to put those abilities to much use they should be able to defeat him.
The following stat block is how I would likely make your bad guy. To be effective he needs to have more allies than a sea cat. Maybe some hired muscle (2*warrior 1). He could even have the protection of wealthy and influential patrons; he is a charming devil after all. In general people will like him, probably more than they will like the PC’s.
His main strength is still skills. He should be able to find out many details about the players. He could seek them out in disguise and talk to them. He could charm one of them and ask questions. He could plant false rumours about them or do evil deeds disguised as one of them. Steal from them or plant stolen items on them for others to find.
In short his agenda should be to mislead the PC’s, get others to perceive the PC’s in a bad light (and perhaps dealing with them without him having to do anything) or even persuade the PC’s to work for him (by misleading, lying and so on.). Direct confrontation should be his last resort.
That’s a bit complicated to pull off, but it will be rewarding when the PC’s finally face down the guy who has been so troublesome.
Human Bard 4; CR 4; Size M; HD 4d6+4; Hp 22; Init +2; Spd 30 ft.; AC 18 (+2dex, +4armor, +2shield); BAB/Grapple +3/+3; Rapier +3 (1d6 18-20*2), Longbow +5 (1d8 20*3); SV Fort +2, Ref +5, Will +2; Str 10, Dex 14, Con 12, Int 13, Wis 8, Cha 16.
Class abilities: Bardic music, bardic knowledge +5, countersong, fascinate, inspire courage +1, Inspire competence
Skills: Bluff +10, Concentration +8, Diplomacy +10, Disguise +7, Gather information +8, Hide +4, Jump +7, Listen +3, Perform +10, Sleight of hand +9, Tumble +9;.
Feats: Spell focus (enchantment), Point blank shot, Rapid shot
Possessions: Longbow +1, Chain shirt, Medium shield
Spells known 0/Dancing lights, Daze, Detect magic, Ghost sound, Prestidigitation, Read magic, 1/Charm person, Cure light wounds, Hideous laughter, 2/Glitterdust, Mirror image
Spells/day: 3/3/1
DC 10+spell level+cha modifier (+1 for enchantments) 13/14/15
Attack with longbow while inspiring courage and within 30 ft. of target
Longbow +6/+6 (1d8+2 20*3)
His combat plan should be firing off the glitterdust if most of his enemies are within area of effect, if not use the mirror image instead. The he should use charm person or hideous laughter on the enemy that seems to be the best fightertype. This should be followed up by inspire courage and attacking with the bow.