The packsize limit does not affect git protocol commands (your push).
From git-config under
pack.packSizeLimit
:
The maximum size of a pack. This setting only affects packing to a file when repacking, i.e. the git:// protocol is unaffected.
When executing a push git will always create exactly one pack no matter the size!
To fix this use two (or more) pushes:
git push remoteB <some previous commit on master>:master
...
git push remoteB <some previous commit after the last one>:master
git push remoteB master
These pushes will all have smaller packs and will succeed.