Firstly, I would just like to say that I admire how you sifted through the information available and managed to learn a lot about this very interesting class. You're doing awesome, and keep it up! ;)
1) Where do you delineate the cutoff for changing arrows? Bodkin = Even Con? Field Point = Con +2? Is there empirical evidence to support what the optimal answer is?
You may find mobs which are more resistant to certain arrow types, but really you have so many other things to be thinking of. applying poisons (not as bad as it used to be). Technically, you probably are right, but so far as what is practical, it might not be worth the extra effort. so yeah, field points are the popular choice.
2) While soloing I use Grandmaster Caustic, GM Fettering and GM Gracelessness and swap in Turger when grouped. Is this the best setup or would you recommend something else?
Conservation works great with the poisons. For soloing, if you want to save on some coin you can certainly get away with non-GM fettering and caustic (drop gracelessness for soloing unless you are doing really hard stuff). Grouped, I run handcrafted caustic, gracelessness and ignorant bliss, unless its a new area and/or the goup is DPS-light.

run warding ebb if your group is mage heavy - it is noticeable.
In T8 you may be able to find an item proc to achieve the benefits you are trying to get from turgur. And with Bylze, and a bit of agressiveness, you can expect a few spikes, so ignorant bliss is a good accessory... haha...
Raid - do what's best for the raid. Usually that just means going the whole night without ripping, so ignorant bliss on the trash and experiment with other stuff on tough nameds. Upgrade your deaggro abilities as much as possible in T8.
3) Is it worth the money/time to run buff potions? Particularly +STR? Would you recommend something?
If you have the coin to be running GM pots all the time, you may get more mileage out of the crit ones, DPS-wise. You can get strength proccing off imbued rings, cloaks, etc. That said, I run handcrafted str 40% of instances and GMSTR 100% on raids. I guess if i get a bad deal on buffs, I usually just resign myself to it in group setting.
Funny, in T7 i could run IINT potions, and I have yet to be able to take it over STR in T8. /cry
Do as many diety quests as you can.4) Do you think that its worth the 40pp+ to get the +12 DPS adornment for the DBoF when I get to 77 or will I not have it long enough (guild group for Fabled epic available) to make it worthwhile?
I am a bylze fan through and through. Not worth the trouble. Are you into transmuting at all. It certainly a good sideline with the copious amounts of crap you will se dropping in RoK and NO-Trade loots you'll be questing for.
Just remember that T8 instances give squat for exp for the time invested so plan to be grinding solo quests for most of your playtime. You should get into RoK as soon as 65 with that lovely bow of yours.
... and i know you said you don''t raid, but their are pick ups around, and you need a X2 mob for Raincaller . Yes, finish this quest now if you haven't already, as it i srquired for your RoK Epic. You have to experience the proc too, it will bring a smile to your face.... though a bigger one comes from making butter out of rhinos at point blank range with your Epic.
Also, do the crafting epic and get the solstice earring which has a 55 runspeed buff (similar to Hadden's Earrign swimming buff) which is good for anything. Make gear macros for soloing and grouping, as there are lots of item effects for soloers in RoK. we should start a thread on those, hehe..
That's all for now.
Canul
<Renegades> AB
EDIT: Oh.. i just remembered i wanted to ask you about your haste item. The darkened guantlets are pretty great item, if you can get a pair.