I agree that they needed something extra at first level, although it was a pretty decent level already. With the two good saves, they get two +2 resist bonuses at first level; good, although not enough to justify the loss of caster level.
Anyway, I went back through to check the balance, and I came up with a few other things you might want to consider:
1> Your new "Imbue Arrows (Magic)" is still phrased awkwardly. You explicitly list the benefits, but not all of them; for example, you don't mention the +1 attack bonus (unless you use the house rule that enhancements on the bow give an attack bonus and those on the arrows give the damage bonus instead of the 3.5 rule?)
Just say "All arrows fired by the Arcane Archer gain a +1 enhancement bonus" and be done with it.
Question: can this be suppressed? If I'm fighting an enemy with DR 5/(NOT magic), can I turn it off?
Nitpick: I've never liked how the GMW spells bypassed the masterwork requirement, or any other characteristics of the material. For example, making Cold Iron arrows magical with this ability wouldn't be any different than normal arrows. You COULD say "all MASTERWORK arrows gain a +1 enhancement bonus; non-masterwork simply gain the ability to bypass X/magic Damage Reduction with no other bonuses"; slightly weaker, of course. Not that this really needs to be changed. If you DID require masterwork arrows, you'd need to add Craft (fletching) and Craft (bowyering) as class skills.
2> On Imbue Arrows (Effect), you want to be careful with the phrasing on the enhancement bonus part. Right now, the way you wrote it implies that it stacks with an enhancement bonus already on the arrow, which means if I fire an arrow already enchanted to +5, I can get into Epic range. You were using words like "cumulative" to imply that it stacks with itself, and it stacks with the Imbue (Magic) ability, but it can't stack with an existing Enhancement or with that of the bow.
Just say something like "All arrows fired by the Arcane Archer gain one of the following abilities: increase the benefits of Imbue (Magic) by +1 (to a maximum of +5), or (all those other +1-equivalent abilities)"
You need the explicit +5 maximum because if all they take for Imbue (Effect) and Enhance Effect is the enhancement bonus boost, they'd be at +6. While "epic" DR isn't +6 any more, it's still not good to have your arrows be better than anything someone could make.
3> Now that I think about it more, Arcane Shot I seems a little on the weak side. Not that it still isn't useful in its current form, of course. My suggestion is to add a flat +1 attack bonus as well (not +1/level, just +1). When using a low-level spell this'll almost be as good as Arcane Shot II. And, it'll actually allow you to trade cantrips for a simple +1 attack bonus (right now you can't trade them for anything).