There are limitations on fatx partitions. Linux can't read 32k or 64k partitions. F is capped at 127 or 137 and g has a cap to but I am unsure of exactly what it is.
There is no problem if you format in ext3 and use it. I think that should work up to 2tb partitions. However the xbox can't read ext3 on the xbox bios side. This just makes your problem exactly opposite than what it is now.
There is a patch you can apply to a 2.4.32 kernel if you rebuild it. This patch is said to make 32k and 64k partitions readable that are fatx. I have been unsuccessful in getting the kernel compilied so I can not verify if it works or not.
Here is a link32k or 64k
And if you are going to go this far you might as well take a look at this patch to. It will allow you to create another partition outside of f or g to put linux on.hd57
As for file size I don't know. I do know that I can put 360 games on the ext3 partitions and it is readable however smb shares don't see files this big coming from samba shares. I can transfer them around but only by ftp.
Hope this helps.