sounds like flower arranging for elderly people with gender issues!
The problem still seems to be audio getting back to earlier stages. It is possible it is through ground line conduction but I'm assuming you have used reasonable construction techniques. I didn't mean to put 100 Ohms in the supply to the audio output stage, only to the stages before it. One resistor and cap in the +12 to the second transistor stage and from that filtered supply, another 100 Ohms and cap to the first stage. I suggest the regeneration control and all +12V to the left of it is fed from after the second 100 Ohm resistor so it is as clean as possible. If you haven't already fitted one, a big electrolytic across the audio output stage supply wouldn't be a bad idea.
Consider than any audio on the supply line will reach the regeneration control and modulate the regen level. I think that's the reason it goes unstable as the output stage draws more current.
Brian.