It probably does have air trapped how can I get that out?
In general:
Yes I do notice some Coolant loss over time.
Is there a visible signs (puddles) or it just mysteriously disappears?
I have not done a combustion gas test.
Well that will depend on the answer above
I haven’t checked the radiator cap but I’ve never seen any leaks from it if that’s what you mean
I meant is the seal in good shape and does the relief spring function.