I checked mobile version and ToS is not on sign-up screen. However, I couldn't sign-up so I can't either confirm or deny that it is/was possible to sign up without checking ToS box. Another thing is, IIRC, FJ did send message to everyone when they changed ToS - does it apply to users who were not forced to agree to ToS in order to use FJ's services? I would say no, but I would also say that it doesn't apply to anyone. If you want people to agree to new terms and conditions - they have to agree by ticking that box, every time changes are made.

Would anyone agree if FJ change ToS and put in there "we will take 50% of your deposit as a fee for our service", doesn't share this with players and simple start taking 50% just because they said they will?  I don't think anyone would.

That is nothing different than any other change in ToS. The rule "we can change our ToS every time we want" is correct, but when they do change it, they need to inform users about it and users need to confirm that they are aware of changes and that they agree with new ToS.

Whatever is not in ToS doesn't apply as a rule.

These are all holes in system and if OP is telling the truth they should hire a lawyer. (of course, if you have received compensation from them and you took it - in that case you should lock this topic, I don't think you have a case then).