What is to be expected of the W when I start the detaching process?
Cadet already got this one nailed. Who knows?

Also in my situation I am able to spend my free time in the basement reading or working on some projects I have. Is that the right option?
Yes and no. How can you do some GAL activities outside of your home? Doing some work on projects is good. How can you also do some things to meet new people and make new friends?

I am concerned I will take it too far and alienate her.
Shes having an affair. What do you mean "alienate" her?

Last night we had supper with the boys, I tucked the older one in and while he fell asleep she sat in front of the fireplace on her phone. I worked in some school work as I am in a trade and doing schooling now. Then took the dog for a walk. She asked how the walk was. I said it was good. And gave a few details. Then I went downstairs and did some work for an hour or so came up for a drink of water and a smoke and she came over and engaged me. I listened and said little.
Listening is good. Validating is good. No real reason to do any more than that.

While I was working she texted me a few times and I have short responses if it was a question.
If you are working, then you dont need to reply right away. You dont want to be doing things just so you dont have to be around her. Dont act like youre avoiding her. So, I wouldnt have your phone by your side ready to reply at a moment's notice.

None of it was a statement. After the drink I went back down and read the forums a bit on my phone and slept. She didn't text me anything and this morning I woke her up as she slept through her alarm. I said good morning and other than that there has been nothing. I just have been talking with my 3 yr old. Do I seem like I on the right path? Or too far. Too little?
Seems like a good start. Now, how can you start doing things outside of the home?