Rule No.# 1
Relax....whatever way you cook it - it will be good. You can move from good - to great in a few short cooks.
Rule No.# 2
TAKE NOTES. Get a spiral bound notebook, and make it you "Cooks' Notes" - and keep it handy. This can evolve into a 3 ring binder with dividers, and clear plastic slip covers for recipes, tips an trips, and your notes about what you did when you las cooked a pork butt, etc.
Rule No. #3
THERE ARE NO RULES....(other than HAVE FUN!) 
But, we are all happy to suggest what has worked for US as individuals. YOUR experience, at YOUR location with YOUR cooker WILL vary from that some, and that makes you an individual, not a "drone" that has to be in locked step with anyone.Hub's Burn it in the Backyard section has some great primers for new-to-pellet-grill folks. And - even I have my own personal formula for pulled pork
http://www.letstalkbbq.com/index.php?topic=869.0 Substitute the rub you have on hand in your case...And - if it has a higher salt content ( look at the order in which the ingredients listed on the label...they legally are listed as the greatest to least...) then don't allow it to rest as long in the fridge. Reduce to overnite if salt content is the first ingredient.
I have looked pork butts fat cap up, down, and on their side just to see what difference it made. And, mine is only one opinion - so your results will tell you if I still suffer from previous head injuries...
but - I se no difference. I think it is because there is SO much marbling of fats throughout the meat - that it will not dry out. And - if you are serving it as pulled pork - you can decide how much fat to trim, and how much to leave as you mix it together in the pan.
One last note about finished IT for pork: Do no fixate on an actual temp. Yes, 195-205F is most often "done". But I have had Boston Butts that were done at 185, and some that had to be cooke to 2015F in order to "pull" properly.
For me - "pulled properly is defined as not mealy or mushy - but no "claws" or forks required to pull the pork. I use insulated gloves ( The Fryer Glove Co. ) and simply work my hand on the meat - and cill come of the bone clean - and the muscle fibulas will separate nicely. You can add a little sauce at this point if that is your desire. When I follow the routine in my above link, I don't need to sauce. If I am too rushed for that - I might add a little sauce. Not for dryness, just added flavors.
Hope this helps. Take notes and pictures and share with us.
Questions
-Does my temp info above look right?
good guidelines. But use a long bamboo skewer or long tooth pick to help you determine doneness once you are in the range of "finished pork temp". The probing should have very little resistance. If you have to really push it in with more than just eh most gentle pressure possible...you may want to give more time. I do not foil pork. It is so fatty it does not need it.-Is it worth spritzing with apple juice every few hours?
Once the meat is coming out of the stall ( ask about this term if you are un-familiar ) I will spritz pork may 2-3 times an hour until it is done. This is also a good time for any small amount of additional "contrasting" rub. Try a blend of 2 part coarse black pepper, 2 part red pepper flake 1 part sea salt and apply it lightly after you have spritzed 2 or 3 times. Then as you continue to spritz - it will "wash" a bit of it in and around the surface of the pork, giving you a bit of extra seasoning to mix into the pork when you pull it.-Should I do some rub mixed with apple juice and inject?
See my link for ideas-what would be planned time per pound based on temps?
This will vary considerably. For my methods...I would budget 14-116 hours for a 10 lb. pork butt. But, this is because I cold smoke at approx 165F-175F on the MAK, then I will stage up temps to usually 275 - 350 toward the end of the cook to create a good "bark"-What would be some great side dish ideas?
In this part of the USA - slaw, BBQ beans, and mac and cheese are common - but - what ever YOU like is best 
-What type of buns for sandwiches?
White bread buns are commonplace. You want the BBQ to shine - and not the bread-Care to leave any other words of wisdom?
I am always short on wisdom...but long on ideas!
