Two Questions Regarding Issues With my Subaru SVX Cooling System

I have a 1996 Subaru SVX with a leaking heater core and I wanted to know or confirm two things.

First of all, I started the car and allowed it to idle up to warm and fluid levels were normal. I came back 3 hours later and found the overflow tank had lost a fair amount fluid but the radiator was full. There was no coolant below the overflow tank and none had leaked from the cap. My question is, while the engine was cooling down, would the leak from the heater core cause the coolant from the overflow tank to displace the leaking coolant? I also found a fair amount of air bubbles in the radiator (after noticing the drop in levels in the overflow tank) and have just burped the system.

I originally thought the car had a bad headgasket because my radiator cap was leaking after replacement but after burping the system and adjusting the fluid levels (overflow was overfilled and radiator was filled all the way to the top), it had stopped leaking from the radiator cap too. After using a combustion leak tester on the radiator, the fluid stayed blue (no exhaust gasses leaking into cooling system). My second question is, if there is air in the radiator (from leaking heater core), would that air build up enough pressure as the engine warms up to break through the radiator cap and let coolant leak out from there?

I am in the process of removing my dash and fixing it up. Additionally, there is no white smoke coming from the exhaust, and while I was burping the system there were no additional bubbles coming from coolant in the radiator filler neck while I was revving it. The oil is fine and levels have not risen as well. Coolant is green and does not have a rainbow colored film above it.

Any help or information is appreciated and thanks in advance!