Recently, i have been getting errors like this, and most of them related with this mod. Hope you can solve it:
crash-2019-08-27_11.44.19-client.txt

That error says you don't have enough memory for Java to do a thing. You've allocated "1060372480 bytes (1011 MB)", which is...way too low for modded mc in general, and I'm honestly shocked vanilla MC will run with it.

Well, that message indicates there isn't enough to reserve..Did you increase the minimum instead of the max?

just tried, but same error:
crash-2019-08-27_21.53.36-client.txt
won't let me assign more memory

"java.lang.OutOfMemoryError: Initializing game"

This isn't a mod error. This is a java and system resources error. I have played ATM3 modpack on a system with 8 gb, so I don't know what is going on with your system, but you need to seek some generalized minecraft assistance.

Maybe run a memtest86 on it, might have a stick of ram that has gone bad.

If i assign 2GB i get this message:
Error occurred during initialization of VM
Could not reserve enough space for 2097152KB object heap
Java HotSpot(TM) Client VM warning: Using incremental CMS is deprecated and will likely be removed in a future release

How much ram is in the system you are trying to play on? You cannot allocate more than you have free.

My laptop has 8 Gb RAM