In family proceedings, each party bears their own costs unless a party acts unreasonably. Your ex is doing the right thing as he is bound by an order that he is now seeking to vary as his circumstances have changed.
Once you have received his financial information you can decide whether to make an offer, or accept his offer to settle on revised terms.
The Form G is a form that is used to indicate to the court whether the first hearing, the FDA, can be used as a FDR - when the Judge will try to assist you in reaching a settlement. If each party is happy that disclosure is complete and no information is outstanding, they both indicate as such on the Form G and you can try to settle at the first hearing.
He has acted completely unreasonably throughout. He text to say I would not be getting any more maintenance and then next thing I know he stops paying maintenance... 3 months now. Then I receive a copy of court papers....