First, your last two paragraphs were good! Focus on you right now. Do not feel bad for stepping out to GAL, but make sure you are still prioritizing your son as well. GAL with kids means to spend as much time with them as possible, but when you aren't that you are busy. Detachment is starting to catch on with you because you are starting to realize that you are going to be okay no matter what! That is important.
One red flag in the last paragraph. Who cares what other females say? This tells me you are looking for validation externally. Know your own worth, no matter what anyone else says and does. Including your WAW, and any other female.
You suspect she might be messaging someone else. And she has been going out and staying out late and getting angry about you questioning that. Assume she is having an affair, but not because that changes what you should be saying and doing DB-wise, but because of your physical health! Stop sleeping with her, you are putting yourself at risk, at least until you are sure there is no one else.
Finally, one 2x4. And you might already know this, but stop being selfish. That is a huge 180 you need to make. I recognize it because I was just like you! Think about it, your W is bedridden recovering from an extremely taxing treatment, and you are feeling sorry for yourself? Even all of your "missing her" statements were about what YOU get out of the relationship. And you haven't even stopped to consider her happiness, that what she is doing right now above all is trying to be happy. All you can think about is how it affects you. And the 10 year anniversary? Why was that up to her? If you wanted to celebrate, despite your discussions on separation, etc, then why didn't you take the lead on that? So recognize the selfish behavior and start working on it. Get into IC. If nothing else, see this as an opportunity to become a better you, for your next relationship (whether with her or someone else).
Hang in there and keep posting!!
M(53), W(54),D(19) M-23, T-25 Bomb Drop - Dec.23, 2017 Ring and Piecing since March 2018