1 35mm roll equals 1 8x10 sheet or 4 4x5s.
Don't fiddle with the times unless you're having problems.
If you go to the Jobo website you should find a piece on using longer times with Fuji film. I don't remember if that was the tetenal setup or Kodak 5litre.
If I understand what you wrote. 250ml per 35mm roll? Or 62.5ml per 4x5 sheet. If you can only use a max of 100ml I'd run one sheet at a time. Will the kit let you mix up odd amounts of chemicals?