In the US, visitation is not optional. The only way a court would deny a parent visitation is if there is a very valid reason for it (ie alcohol, drugs, abuse, etc), and even then they would likely get supervised visitation.
The spouse cannot refuse visitation, however the courts can.
No, a stepfather will not have visitation rights to his stepson after a divorce. The mother can always allow the stepfather to visit if she wants.
Many states allow stepparent visitation rights
Women and men alike have the same rights in all 50 states when filing for divorce. Gender doesn't matter.
It the non custodial parent alters the court ordered visitation, the other parent does not have to allow the visitation, unless it was altered in court. If it was not altered in court, the parent can file for contempt of court.
A married person can claim adultery as a grounds for divorce if it is legal grounds for divorce in their jurisdiction.
It varies by state and depends on the parties. Many states will allow the parties to then sign an agreement resolving all issues and finalize the divorce in as short as 30 days. In other cases, a couple may opt to litigate the issues (such as division of assets or custody/visitation) and may find themselves caught up in the court system for 1-2 years or more.
Some states allow a "legal separation" instead of or before a divorce, which could include alimony and/or child support. In all states, I believe, you can file for divorce and ask for temporary child support and/or alimony pending the divorce. Check with a lawyer in your state.
it depends on where you live because some states won't allow it.
In the US, child support and visitation are two separate things. You are legally responsible for financially supporting your child rather you have visitation or not. If your ex refuses to allow visitation then you need to petition for court-ordered visitation. If you obtain that and the ex still refuses, then s/he is in violation of a court order and there are consequences for that. If, on the other hand, you don't have visitation because the court refuses to allow it (for whatever reason)...well, that's a different issue.
Sue him or take him to court
Getting a divorce will depending on the state that you live. Some states may require a period of separation before divorce, while other will allow the couple to move forward with divorce only.