1. If you don't care much about the fish and are not doing extensive, heavy rock work, then your PVC liner will probably be fine for a few years. When it kicks the can, you can replace it with something better. If you care, I would swap for EPDM or RPE before it's too late. Lots of horror stories with PVC liners. For what it's worth, though, I built a PVC lined pond with my dad when I was a kid and it lasted probably 10 years.
2. Raccoons are wiley buggers. My pond has nothing but a few inches of rain water in it right now, and I find a new set a prints traipsing through the water almost daily. Had one little guy in there last night. Must have scared himself. Made a horrible noise while panicking to get out. Scared me too!
3. The equation for liner size is very simple. To determine length: Length + 2x max depth + 2. The +2 is to give you a foot of extra to work with on each side. The bigger the pond, the more extra you should give yourself for adjustment—you find ways to use it! Same equation for width. Keep in mind that this equation fails if, at any part of your pond, you have a hump to go over. If so, factor in the up + down of the hump. Then add a little more again because there is no such thing as a liner stretcher.