You won't like this. The measurements you got are both short. By a good amount.
The 22016700 rear absorber, new, clocks in at 4-5/8" measured to the bumper face to the frame face, just like you measured yours in the pic.
In contrast, and just for the heckuvit, I measured a new Cutlass front absorber 22016704, and it clocks in at 6-1/8" same measurement points. Point is, I got a feeling these will be a hair variable, as they put shims in there to adjust the bumper out as needed. But you need to be about 4.5" on the rears and 6" thereabouts on the fronts.
Unfortunately, there's no "spec" that I can find on them other than compressing them 3/8" of an inch and if they return to normal, fine. If not, replace.
Under the GM guidelines, yours would need replacing. BUT, the problem is, where you going to find them? Not at GM anymore, and hard as heck to find them.
Anyway, there's your measurements. There's an orifice rod in there that controls how much fluid gets transferred to the outer side of the unit's piston and how fast it travels through the orifice when there is a collision. It's possible you can slowly force the piston/cylinder apart to 4.5" -ish and re-use it. If it won't go to at least 4.5", I'd probably try to think of something different.
SLIGHT dampness around the seals or crimp seals in back, etc., isn't considered a big deal. Constant dripping is.
79-85 E and 82-85 K body (Eldorado and Seville) Cadillac rear uses the 700, as does the buick G-body 2-door and Olds G-body 2-door and wagon 78-88. Buick and Olds interchange with the fronts (704) too. 78-81 Malibu wagon uses the 700s in the rear as well.
Good luck.