So I'm glad that at least the 2 Arduino setup works! Tomorrow I'll solder my 3rd and last pcb together, this time with an ATtiny85, as soon as I checked with a DIP package on a breadboard, that it actually works with one, since it's probably only maxed out. Sounds like a good idea. I might throw in a pullup for the reset line and a 100nF cap from VCC to GND as well. Should add that onto the pcb. Hm..

Off to bed now, happy hacking!