Could I be making the biggest mistake of my life?

Hi all, I'm new here and hoping to get some really good advice on a situation I've landed myself in. I'm married with 2 children one 4 and the other 14 weeks. Me and my wife always being rocky, we always argue and she's always threatening to kick me out of our house. Anyway after years of this I've had enough of it and at the weekend she said I need to leave and I obliged and said that I also think it's for the best and off I went. She then got upset and wanted me to come back. We have so little in common and the only strong thing we both want together is to achieve things in life, it's having a nice house, lovely family, car and good careers. Well now we have that we have nothing. Here's the predicament. I'm 32 years old and feel I'm young... Lol? And as I've had enough over the years I've been more and more worn down. She's really not nice to me and speaks to me like crap and she has complete control, I have to hide that I smoke, I know that's wrong but she hates it and I'm not prepared to give it up, if I wanted a glass of wine at night she would question it. The other week a 24 year old woman from work recently joined a team I manage she has 2 kids and is going through a really tough time, I've supported her through these and continue too and you guessed... We now are starting to really like each other. She accepts me for who I am, she's on my level and I'm really attracted to her personality. Due to work we speak 5 days a week (via teams) and she coming to meet me for the first time next week for a brew. My family don't really like my wife and because of how she is I don't speak to half the family. Asking them for advice would be stupid. Just before Christmas my wife nearly died from a ruptured appendix I can't believe at this stage of the year so soon I'm feeling the way I am. After being there for her all the way through. The last part is the bit that hurts, leaving my children would absolutely kill me inside I would literally have no money and have to live at my mum's until I could move in with the person I left everything for. My wife has also started to make an effort to get close to me, but I'm not interested. I earn £2200 after deductions and after having to pay her maintenance and my half of the mortgage I'm left with £809 a month that's absolutely nothing but I don't feel like I care. All I think about inside is this new woman and I feel so so anxious. I can't eat correctly and trust me I love my food. I don't want to hurt anyone especially my kids, but how long until things go back to normal at home and hating each other. I get you all think I'm doing wrong but I honestly appreciate all advice. After years of feeling the way I do I'm not surprised this has happened. Thanks in advance Danny