Thanks for all the answers and support! The number of replies exceeded my expectations by far - a very supportive community I find myself in.
Now about the progress:
- we did make it into orbit on another profile, one I play with my daughter, just using a shorter, stubbier rocket, mimicking the Vostok we built the first stage as 4 liquid fuel boosters on the sides, second as a single liquid fuel rocket at the core and third as the capsule with the smaller liquid fuel engine and just two fuel tanks,
- I suspected the fins/winglets I have did not have control surfaces, so on that rocket did include just one set of 4 at the bottom,
- I didn't realize the LV-T30 has no gimbal, I assumed all liquid fuel engines in the program do have this - that would explain why my rocket was so hard to control.