There are no reservation for non group camping, its first come first served. Try reaching early during the day (as early as possible) if there are any left. One can keep campsite minimum of 14 days dependimg on campsite so its little luck as well

Yes

YES - Jackson lake has excellent fishing for Lake Trout. The lake is "utilized" extensively (it's fished heavily) but consistenly provides great fishing.

Yes, the Lakefront Retreats, Two Room Bungalow and Home Away From Home have Kitchen along with Coffee Makers, basic pots and Pans and basic utensils. The country Rooms also have a coffee maker but no kitchen or utensils.

I am not sure about the rooms, but other facilities such as showers, restrooms and laundry rooms are. However if you contact the park they will be able to let you know. I would beleive they are ADA compliant as they receive federal funding.