At the end of your log, there is this line:
[B#339] Picked up _JAVA_OPTIONS: -Xmx512M
The problem you are encountering is caused by a java environment variable which limits all java processes to 512 MB max.
Even though you might think to prevent this by just ramping your RAM usage up in the launcher, this environment variable just happily overrides that.
Please join the Technic discord chat, and ask in the #help channel how to remove the Java environment variable. This happens quite often, so no worries.
JaariAtmc got a reaction from jumpandshootbeef in Allocated heap space bug(?)