Partner of 7 years cheated

NSFW tage just in case:

I am currently engaged to my partner of seven years.
We were long distance for five and have been living together for two years.
I found out tonight that when we were long distance, about 3 years into our relationship, he had solicited some women on reddit to sext with him.
He never physically cheated and told me they never exchanged nudes.
The accounts I found had been inactive since I moved in with him.

He admitted to having a porn addiction that escalated to soliciting people online for NSFW chats and roleplays.
It isn’t an excuse but an explanation of how he got there.
He agreed to deleting the accounts and showed me he did.
He also said I can look at his phone whenever but I don’t plan on playing security guard and checking his phone 24/7 as that sounds unproductive for both of us.
He is starting a new job soon and wants to also do couples counseling.
I want to stay with him.
I genuinely believe he is my soulmate.

If anyone who has had a relationship recover from infidelity would share any advice I would greatly appreciate it.
I don’t want to hear any advice that ends in “Leave him.” Or “He’ll do it again.”, this is unhelpful to me.
I want to know how I can work towards forgiving him and how we can rebuild together.
I know it will be a lot of work for both of us but we are willing to put in the effort.

I’ll answer any questions and would appreciate input.
Thank you.