Divorced. My fault, and cant move forward

[MrBond]

"Should I be trying to interact with him when doing the NC?"

You have an 8 year old son together. Let's face it, you're NEVER going to be total NC.

"The only time my therapist said I should was only concerning my son."

Yes, that's how it should start. There should also be a few times when he sees the two of you together to lend him support.

"Should that contact be in person, or via the phone? "

It could start off on the phone. For example, my W and I had an arrangement where we would have our Ds call the person whom they weren't with every night at 8. I would pick up the phone and after a few times of leaving it strictly business, I started asking my W how her day was. At first she was leery about this, but then eventually opened up. Then we started hanging out, etc.