You can't stop paying on your own but you have good reasons to seek a judge to order you to stop paying. So you should get into court to address...

Can support be based on previous income if father is collecting unemployment & working under the table without reporting pay?

Yes the party's earning capacity is key not the present income.

My ex and I share custody of my daughter, 11. My ex has a 14yr old from his previous marriage and he shares custody of her as we

If you mean be with her to mean live together yes if there are adults.

What can I do???

If you are worried about harm to the child then get into court to modify parenting time.

What can I do to get the money that was agreed upon in my divorce.

You need to file an application in court to enforce your rights.

Divorce proceedings in post-ESP. How to change lawyer?

It's simple. You tell your lawyer they are done and you hire a new one. You run the show.

What are my legal rights? Is it legal for her to take and show nude pictures of me to anyone?

You have an absolute privacy interest that you may want to consider protecting and there are numerous other statues that are implicated.

Can he seek a reduction in support based on her added income?

Not likely however his income may not be enough to cause any appreciable increase.

My 401k plan is she entitled to what I have put in or matching funds from company also

Everything from The date of marriage to the date of the complaint filing

Yes to help you otherwise what sense does silence make?