I currently have a torrent which has 15 folders in it. I am downloading each folder one at at time in seperate sessions by removing and retorrenting it so that i do not overstress my storage device. However, once i am done with the last folder in the torrent i do want to continue seeding the torrent so that others have an easier time. My question is, will tixati automatically seed the entire torrent even if i am only downloading a part of it? or will it only seed for the part that i downloaded and not the entire 15 folders.

It will seed whatever it finds in correct state on the disk. I.e. you can start seeding a file if you put it where Tixati expects it to be:

1) Upon adding the torrent you point to the correct folder with correct folder structure - Works

2) Add torrent, stop it. Replace the empty placeholder files where Tixati would download to. Start the torrent. Tixati will do a quick verification and start seeding. - Works. I'd still recommend a manual Force Check

Also what you are doing is pointless. That's like trying to drive an electric car in manual transmission mode. Just limit the download bandwidth. Or untick the folders under Files and when the last enabled folder completes enable the next folder.