Minecraft uses whole module (single thread for regular CPUs) and nor CPU, nor RAM, nor GPU are still not fully loaded. I doubt that AV would cause memory and CPU hoarding in menu.
That’s lowest possible render distance (2) and none difference to FPS.
EDIT:
Tried on other PC with win7, everything is OK. Deleted all other versions of Java (exept jdk-10.0.2). Still same memory leak. 32bit version won’t even start runoutofmemory(). Any ideas where to look?
EDIT2:
Reinstalled video drivers, no difference on cpu and memory consumption.