Re: Memory keeps increasing causing a restart

[Rick James]

This might be a problem:
myisam_sort_buffer_size 3221225472

This is too large (but won't explain your problem):
( query_cache_size ) = 256M -- Size of QC
I recommend no more than 50M

This is dangerously big, since may be allocated for some queries -- such as your summary tables:
( tmp_table_size ) = 1,000,000,000
(I would guess this is the problem.) 100M is more reasonable.

Overkill:
( thread_cache_size ) = 16,384 -- How many extra processes to keep around (Not relevant when using thread pooling) (Autosized as of 5.6.8; based on max_connections) 0 is a good number for Windows.

Do you load the nightly data into a temporary table, massage it, extract summary info, then put it into the big Fact table? Or is the ETL done some other way?

Please provide
SHOW GLOBAL STATUS;
so I can dig further.