Hiking and backpacking is one of my hobbies, one that I participate in more than shooting. I've been hiking and camping since Scouts, and I consider myself moderately experienced.
I see a dilemma with your stated goals. One one hand, you say you want to hike more and stay out longer. On the other, you want to use inexpensive mil-surp gear and carry a 8.8lb rifle plus ammo.
Backpackers, by and large, have a less is more philosophy. If you have less weight on your back, you will be able to go farther, get there faster, and do it more comfortably. My all up load for a 1-2 night trip is in the neighborhood of 30-35lbs, and that's taking into account my chronic over-packing.
If you were to take your SKS and the pack that Regolith linked to, which did look like a nice pack for a hunter packing a few miles into a basecamp, you would already be packing 21.6lbs. Start adding in tent, sleeping bag, cooking gear, filter, food, clothing, etc, and you're going to end up with a
heavy pack.
If you take the less-is-more route: Pick up a decent pack from REI or similar. I prefer an internal frame, but packing an external frame can be simpler and they also transfer weight a bit better. This
Kelty pack from REI weighs 5.5 lbs, and should have plenty of capacity for a multi-day trip. Add a .22 pistol or whatever handgun you feel like, call it 3 lbs for a gun and ammo. Now you're starting at nine-ish pounds, as opposed to over 21 lbs. That right there is like taking six quarts of water out of your load.
By cutting significant weight out of your potentially heaviest items you are going to be able to hike longer and farther, more comfortably, while carrying more food so you can stay out longer.