Ex wont leave me along..

There's plenty of options:
- set firm boundaries
- learn to respectfully but firmly assert yourself
- if you aren't good at those, learn & practice (take classes, read books, get counselling, search youtube etc + put what you learn into practice)
- get support (friends. family, etc)
- explain what is going on to your children / explain how you are handling things to your children

If you don't want him constantly ringing you:
- set boundaries on how many times a week he/she can call you' or
- filter everything through voicemail; or
- insist he/she only contact you via email (excepting emergencies), and read your email once a day

etc

Not sure why your ex would commit to you...

Do you want him to commit to you? (I didn't understand why you said that either).

I have a parenting agreement with my ex that specifies times and responsibilities of each of us with our daughter. I pick up my daughter, maybe spend 3 or 4 minutes talking to her mother about parenting things (schedule, who will buy clothes, playdates, etc.). Then I leave with my daughter and no drama. I do not enter the house of my ex-wife (except in rare occasions like birthday parties where we are both involved).

You can set legal limits. Parenting agreements can be enforced using the court. If you want to do this, you should talk to a lawyer. I don't know if you are there yet.

Other than that, you should set very clear limits that make you feel comfortable. I think it is completely reasonable for you to insist that he not enter your house. When it is his time to be with his daughter, he can take her to his house, or somewhere else.

My ex husband wouldn't stay out of my personal business. Try parallel parenting. A google search will give you advice on how to implement it. It's hard trying to not let it get to you but the sooner you show him he's not bothering you the sooner he will realize that he no longer has a hold on you.