The rubber seal outside the piston might be worn and grease with dirt from your cv boot might sneak into there already. When you use c-clamp to push piston in, you should clamp on the brake pad and it's okay to do it.

Well I did it on the pad when the caliper was still mounted to help get it off the router, but then i had to compress it a little bit more without the pad on to get it flat enough. I think I put the round floating part of the clamp in the middle of the piston. Maybe that did f it up? Didn't seem like it and the others are fine i did it the same way. DIY didn't mention anything special here and I had done this once before when I did the cv boot repair without issue. They were all a little bit dirty, I tried to clean them off with air compressor air gun tool as best I could.

Is there a certifiable way to tell if it's the caliper? Maybe the heat thing?

OK - I'll try that too. If it's seized it will not be gripping at all? What about compressing the piston with the c-clamp then pressing the brake pedal to see if it tightens up?

Can the calipers be switched side to side to see if the problem moves? Worst case scenario how much is a new one or can they be repaired? What about aftermarket, perhaps something stronger? Probably won't work with the rotrs I got.

After reading a bit I found some interesting info and things to try on an e46 site:

http://forum.e46fanatics.com/showthread.php?t=571942

Some techniques that are definately worth trying. I assume the piston can seize either in the open or closed position? Also answers my question about whether or not the caliper can be repaired, it seems that there are seal kits for them and they can sometimes be salvaged. Whether or not I would want to roll the dice on a safety device is another thing lol.

Also searching on this site for provides a wealth of information, a lot of people who have had a simialar issue such as this.

IF I do have a frozen piston - is it possible I warped the rotors already? Both fronts or just if one side was dragging? If so can they be machined or sanded down and re-used? I can't imagine that this few miles could have done anything yet...

Can i determine this using my digital micrometer?

Well i haven't done my tests yet but i am thinking frozen caliper makes the most sense here. everything was fine before. I did some searching and at least replacing with a reman unit wont be that pricy. About $55 after core refund here. Repair kit is about $25 and probably not worth the time and frustrations. If it ends up being the problem gives me a good reason to bleed and install SS lines maybe.

So where can I get some SS lines?

I just tried shaking the front wheels with the front end on stands. They seem pretty solid. The pass side seems like it might be have a tiny bit more play but really for the most part is really firm.

How much is too much play? Should it be noticeable? Obvious?

One thing I have notices is when i drive the car and go over a speed bump with the passenger side there is some squeaking sounds. I don't think the pass side is doing that.

I am going to do the other tests that have been mentioned in my other thread.