I'm concerned there's something here I'm missing.
The Indy should have been able to tell you that a bit of lift is normal. Normal suspensions "droop" when on a lift and should have some play in them before you start compressing the coil (which he wouldn't be able to do tackling-dummy style). That he didn't or wouldn't tell you this bugs me. He's either inexperienced, disinterested in working on the car or scared of it.
Coils rarely fail catastrophically, at most they lose a bit of spring... but that loss probably isn't a big deal for a street car. Unless the extra money isn't important to you or you need to pay for them for piece of mind, I wouldn't replace them. When they fail catastrophically you hear scraping and see it broken and that corner of the car is lower. You'd notice this, I believe.
Struts, you always replace in pairs, so doesn't matter if the hard to push or easy to push one is at fault, you're replacing both of them.
I'm going through the same as you. My car had a clunk that could not be found. I took it to a BMW Indy and my struts are so bad that when you compress them, they "catch" and will hold the assembly up against gravity. The inside of the struts have hard parts catching on each other, there is no more hydraulic action.
You're going to be hit with 2-3 hours labor PLUS you'll need an alignment when they're done.