If there is a leak somewhere, shouldn’t there be fluid present? I’m not a mechanic, and I wish I had the answer for you, but if there is a leak, there definitely should be an area where the fluid is escaping from. Does the fluid level in the MC drop over time? I know you just ordered a used set of calipers, but if the originals aren’t leaking, then they shouldn’t be the problem. Just my 2 cents. (which has an actual value of 1.5)
P.S. I keep hoping that every time I see an update to this thread, it is you declaring your success, so don’t give up! We’re rooting for ya!