Our ISO25 was very fine-grained, comparable to traditional ISO100ish films like Plus-X or APX100. So, you lose "only" two stops by making your own, old-style emulsion compared to modern commercial products. 2 stops only, it's not so bad, completely usable!
Not so bad at all! I really, really hope you start cooking again.
re The Formulary's subbed film: 7 mil is perfect for sheet film. It's too thick for roll film.