Unfortunately, with the a arm design utilizing separate coil springs and shocks, the only way to really get lift with this is either to force a longer spring or using a higher spring rate in the front. (Or you can take the expensive route and convert to adjustable coilovers)
Both of these options will greatly change the characteristics of the front end. Longer springs than what it's designed for will increase the chance of coil bind on large impacts. Higher spring rates will get you lift, but greatly increase the stiffness in the front end.
What are your plans for this truck?
1. Shake lift? Never heard of that unless you mean a shackle lift. The way the rear suspension is designed in these trucks is that the rear shackle mounts underneath the top of the spring. This means that you cannot simply purchase a longer shackle and install that to increase the rear lift, it will do the exact opposite and lower the rear end of the truck (if it actually fits). To allow for the ease of changing the height using shackles, Offroad Design and DIY4X both offer shackle flip kits. These mounts replace the factory rear spring shackle mounts and convert the rear end to using and above the spring shackle orientation.
2. If I remember correctly, the 1 ton spring lift works because it's a higher spring rate (more leaves in the pack) as well as utilizing longer springs. Also, I do believe that the 1 ton springs are actually narrower than the 1/2 & 3/4 ton trucks. I don't think this is a direct bolt in solution considering that your truck more than likely has 52" rear springs whereas the 1 tons are 56"
3. No one is regularly trying to lift a 2wd squarebody, thus no aftermarket support for those parts. If you can measure out the current coil springs, you can probably find a spring from another vehicle with similar dimensions and spring rate.
4. The gas tank doesn't have much further to move upwards without adding a body lift and/or modifications to the cab and bed.
5. Trucks are normally designed with a small amount of rake when unladen. This gives them better driving and braking characteristics when actually having a loaded bed since it will hold the vehicle pretty close to level instead of dragging the rear bumper everywhere.
Now for your requests:
1. Again, not many customers would purchase a 2wd lift kit. Instead, it's the exact opposite in that many 2wd owners would rather level or drop their trucks a small amount to go for a hot rod stance.
2. With the truck already having a small rake towards the front, using a smaller lift in the front and a larger lift in the rear will only further increase the angle of rake. To get it closer to level, you will have to use a larger lift in the front than the rear.
3. To achieve a lift without increasing the ride stiffness will require an entire reworking of the suspension. Will depend a lot on careful consideration of all parts that will be going into the suspension.
4. Depends on everyone's idea of affordable. Can easily range from approximately $5-600 (retrofitting parts from other vehicles) up to over 3-5k if you need coilovers, shackle flip, new springs, etc.
5. Sadly, it will be a pretty poor choice to take a 2wd truck out to go play in any amount of mud that's more than a dirt road that had just been drizzled on. Not only are you missing an entire drive axle, but unless you're planning on lsd, spool, or an actual locker, you will have only a single drive wheel. Ever seen the movie My Cousin Vinny? Remember the part where they spent the night in the car out in the field while it was raining? What happened when they got up to try to go back into town? Foot to the floor and a single wheel was just shooting mud everywhere and all over Joe Pesci. Exact same scenario of a 2wd truck out in the mud. Get stuck so easily without major modifications.