How much Abuse can a model 20 w/ 2 piece axle take

No truth at all. For one, that key in the axle/hub is so it aligns the same as it came off, it's not for strength. You do need to do one at a time or mark them so you get the hub back on the axle it came off of. When first installed the hub has no splines inside -- it's smooth until installed on the axle, which is harder and forms the mating splines in the hub when torqued down. Mix the hubs and the splines may not match, and they are fine -- not enough room to form new splines strong enough to hold if you drive hard.

Torquing the axle nut is the second part of the equation. That nut needs to be torqued to 250 ft/lbs. Not many have a wrench they can do that with. If you just put the hub back on and tighten as much as you can, it may not be enough. In that case you will eventually spin the hub. How soon depends on the type of driving you do and just how close to 250 ft/lbs you are. Cruising around? Might never spin. Four wheeling? Will probably spin it on the first outing -- same with drag racing. It's okay to go up to about 300 ft/lbs, but I wouldn't go any more than that. There is also a "stick out" measurement for the end of the axle. That may require torquing a little more to get the hub back enough. If that happens you should torque down to the stick-out measurement then loosen the nut and torque back to 250-300 ft/lbs and check the measurement again, leave it if at the measurement.

If you broke spring perches and the axles held I think your hubs are fine now! Of course if the springs u-bolts were a little loose that would contribute to breaking the perches...

The good news is i have access to a 50 ton press..Ideally here I am looking for a quick fix of a leak. Does anything usually get destroyed when separating the two? I am going to have to find a 300 ft lb torque wrench.. We do have some 250 around the shop but atleast in the aircraft world we wouldnt ever max out the torque values and no one is going to let me take home their wrench anyway. I know i wouldnt lend one of mine out either.

Couple of things. I think that 4 wheeling with big diameter knobbies is going to break things pretty quick, but a street car is little or no issue. First of all, re-read Farna's post. There is a procedure for installing new hubs to cut the splines correctly, and then there is torquing down to 250. Check the TSM and follow it and you should be ok. This is in a street car with reasonable tires. 

Great info.. Thanks

you need to press it back on, the nut alone will not press it on tight enough. If you are going to abuse it.