Hi Sagittarius, welcome to the board!
I' m sure you' ll get plenty of answers to your questions. There are alot of knowledgable folks here.
Opinion 1: PSE bows are proprietary, and only work with PSE sights, rests, etc. Is this true?
This is false. Sights, rests, quivers,etc. are interchangable. PSE does offer their own accessories but you are not limited to them.
Question 1: What is a good way to measure your draw length?
The best way is to visit a pro shop. They will be able to get an accurate measurement.
Opinion2: longer bows are better for a novice. True? What constitutes a longer bow? 34 inch or more axle to axle?
Longer bows are more forgiving but doesn' t necessarily mean it' s better for a novice. The best bow is the one that feels best to you. From this board you can get a few opinions on what bows to try out. But you really should try them out and see which one fits you best.
Question 2: This one is pretty loaded. Can one buy a decent setup including all accessories for less that $500?
You can buy a decent setup for half that! (Minus arrows) Cabelas and Bass Pro shops both offer complete packages that would be great to start out with. But if you' re willing to spend up to $500 you can get a really nice setup. PSE, High Country, Darton, Browning, Reflex, etc. All make good bows easily within your range.