Welcome DJH. Sorry you are here but really glad at the same time because you have come to the right place if you are wanting to save your marriage but more importantly, save yourself. I know you are really struggling right now. I’ve been there. We all have.
First of all... I don’t think there is no hope in saving your marriage. Reading what you wrote, I think there is a lot of hope. HOWEVER, I do think the situation will become hopeless if you keep doing what you are doing. You need to stop right now. As hard as it is, you need to take your focus off of your wife and put it squarely onto you. Understand that doing nothing is way, way, way better than doing anything that gets perceived as pressure by your wife. No more letters. No more texts asking her what she is doing or where she is. Your texts should only be about your daughter and even those should be limited. Your wife needs to miss you. She can’t do that if you are always in her face reminding her you are there. She knows this. Let her go to get her back. And when you see her, don’t tell her you have changed, show her. And stop with the flowers and gifts. That is just more pressure.
I know you are driving yourself crazy thinking about her with another guy. Stop doing that. You are only torturing yourself and there is a very, very good chance that the reality and what you are imagining are very different. You don’t know what is going on so stop torturing yourself. Easier said than done, I know, but you are not helping yourself. You need to find a way to detach. Work on it as if your life depends on it because it does at this point.
When you find yourself wanting to send her something or call her or do anything to contact her... come on here and post about it instead. If you can follow this one rule, you will be way ahead of the game. Read as many threads as you can. This will help you immensely.
I could write more but that’s enough for now. Others will be along soon, I’m sure. Hang in there. You can do this! (((HUGS)))