It would be good to see the full area of the actual negatives including the rebate. Scanning, cropping, and flipping to positive can introduce defects or hide them. Assorted comments:
Exposure maybe a bit heavy. I would expose Fomapan 100 at 1/8 sec at f16 on a light overcast day.
Film may be fogged (age, heat, ?) in the box. Develop and fix an unexposed sheet. It will come out even all over if the film is good.
There may be a light leak in camera or film holder.
5 minute development (which dilution?) seems inadequate. Ilfosol3 loses activity quickly once the bottle is opened, at least in my experience.
I would never use stop bath for film, just a couple of water rinses between developer and fixer.
Fixing time seems short. 4 minutes is marginally ok for fresh Ilford fixer mixed 1+4 and well agitated 10 seconds every 30 seconds but old/tired/1+9 fix needs more time.
I would never use "washaid" for film, simply unnecessary, just a 15 minute wash in gently moving water.
The last step should be a wetting agent like ILFOTOL or PhotoFlo so the film dries evenly when hung up to drain. No squeegee or wipe.
Good luck with the above guesswork. I fear problems like these can take half an hour to solve in a darkroom or half a year on the internet.