@newtzy5ive
Advice?
Start thinking with your head and taking responsibility for yourself instead of wanting to be "rescued". That means finding your own place and making an alternative home for you and your children. If you do that, there is a very decent chance of preserving your relationship with your children. If you think with other parts of your anatomy, as you're currently doing, you will cause extreme pain and distress to your children who will have been abandoned by their mother so she can move in with her BF. That damage may never be repaired. Your children shouldn't be required to pay that price.
It's distressing to be miserable in your marriage. Ideally you would have left under your own steam but, for many people, falling for someone else is what galvanises them to leave their unhappy marriage.
Remember that at the moment, your BF is looking very shiny and new; time spent with him and sex with him have the added piquancy and excitement of the fact that you're not supposed to be together and therefore you have to snatch these moments to be together. Also, the comparison with your H in your miserable marriage is probably very flattering for your BF. I know of a few affairs which have turned into very contented and secure LTRs and the parties are still together decades later. That might be the case with your BF. But equally, this new relationship could crash and burn.
You surely don't want to smash up your children's hearts for any reason (because, have no doubt, having their mother choose a BF over them in the way that you're proposing will smash up their hearts) but in particular you don't want to have done it for a relationship which peters out.
If this new man loves you, he will wait for you while you extricate yourself from your marriage, find a new home for yourself and organise shared custody of your children. If he won't wait for you while you do that, then he doesn't love you.
You're 49 and you're a mother. Be sensible and mature about this, OP; don't act like a giddy teenager.