1. If you want to have SFU, ask if they will give you an SFU ending and not HGU.
2. These endings have a user account so that the users themselves can change redirects and not bother the operator. After all, that's what GPON was invented for, and it has an advantage over EPON. I am very surprised that the operator apparently does not use this advantage in technology in your case.
Ask for a password to the user's account, if they are available.
Probably 95% of subscribers did not understand anything from what I wrote - use uncle google and wikipedia

3. Do not give the default admin passwords to users, because this may only end up in trouble for this subscriber both on the program and criminal level Art. 267kk.
4. If you wanted to have IPzew (rather it's a standard in my area), you had to ask the operator about it before signing the contract. The redirect is the same now and I do not moan as I do. If the operator does not want to share it, he will secure it so that the tricks will not help you - take his word for it. As these interlocutors said, consult the operator on these matters.
5. H660GM as a grommet?

Good ... This is what I do not understand at all, why the operator uses the device for at least PLN 300 as a via ;)
By the way, it's a bit strange you have this operator

but I don't go into its economy anymore.