The only thing you can really do to prepare would be to read all of the pleadings and rehearse a statement to the court based on what they contain. It is a document only calendar, so no new information can be introduced (only the information in the documents).
You do not get a strict reply to his response to petition. You do get a strict reply to his response to your motion for temporary orders though. If he didn't serve you, but you can get a copy and get your reply in on time you can do that. You can also show up to the hearing and ask for a continuance for more time to put your strict reply together.
It sounds like the offer that was made to you was a proposal and that it may no longer be on the table. Your options are to go forward with your current attorney and take their advice, fire them and hire a new attorney, or fire them and go forward unrepresented and work directly with his attorney.
Agree with the above. There is no set amount of time an offer is good for. Without knowing more about your case it is impossible to tell you why it was withdrawn. Perhaps ask your attorney as they know your case best.
You seem to have a lot of complicated questions that can't really be answered over the internet. Your best bet will be to get a second opinion from another attorney. Bring all of the paperwork you have so they can go over everything with you.
At the very least, call around and schedule a few one hour consultations with attorneys in your area as a first step. They can point you in the right direction. Some will charge a fee for the consultation, others may do them for free. Use this website as a resource and start calling around.