Is where my son stays enough to get custody?

Yes, you have a chance. But the outcome of cases can be unpredictable.

Divorce question

See the website www.uncontesteddivorceinillnois.com. That has many of the answers you seek.

Can my wife change our custody agreement, steps to prove me unfit and can I contest a felon moving in with my children?

To answer the three questions in your headline: yes, yes, yes.

Is there any way to get round this requirement?

Your question does not provide enough facts for me to answer.

Yes. An employer can refuse to hire someone for any reason, so long as that reason is not illegal.

What rights does my exes wife have of my daughter? He has full custody

You have not provided any facts that indicate your ex's wife has any "rights" to your daughter.

Can my soon to be ex wife keep my kids from me because I am currently dating.

Yes - she can. . . unless you get a court order for parenting time.

No notice of hearing given

Your story is a cautionary tale to all those who thing about opening the door for the police- it is almost always a bad idea to open the door for...

What will a judge likely do with my case?

It depends if you can prove the drug and alcohol impacts the children. It is somewhat unpredictable what parenting time will set.

Was billed for initial consultation in which I was trying to understand the process of working with a mediator for divorce.

A mediator is a "neutral" that helps people reach agreement. See the website www.divorcemediationinillinois.com for more about that.