Sounds like much of your need centers around rough cut mowing, Bush hog, type of work. A general guide line is 5
pto hp, not to be confused with total
hp, per foot of mower. So as an example, most 35
hp tractors will have somewhere near 30
PTO hp and will run a 6' rotary mower. Unless you plan to work a very limited amount of the 80 acres I wouldn't look at anything smaller.
A tractor with 4 wd will help in your more challenging terrain, power steering is a big plus, a
FEL (front end loader) will be more valuable than you can now imagine and a shuttle shift gear transmission or a hydrostatic transmission will be easier to operate for a new owner.
MarkV