When I try to create .torrent file in my seedbox for 75GB file I get 6MB .torrent file and cannot upload it cuz its too big...
What should I do?

Set the size to 8 or 16 instad of 1-2 and/or split the torrent guess you are talking of rared tings, and some trackers don't allow fx 2000+ files in a torrent

If you want help you have to be more specific like:
I try to create a 75 gb torrent that is splitted into 12.000 rar files
I used the following program (utorrent rutorrent déluge tranmission)
With thise settings private torrent / start seeding / and pize side fx 1

in other words, increase the piece size to higher value, than default.