E.N.
I don't know how to offer advice for all that you are dealing with right now, but I can tell you that you can still be very close and bonded with your son, even if he weens now. I did not get to nurse either of my two babies for very long at all (only a few weeks), they are 3-1/2 and 2-1/2 years old now, and I feel very close and bonded with them, even moreso now than when they were babies and I had lots of time to hold them and snuggle. Our bond continues to grow and matures, as they also grow and mature. When my boys were in the early toddler phase, there was not much I could do to get them to slow down and snuggle, but they would usually sit for just a couple of minutes with me to read a book. Now they will sit for 1/2 hour or more and snuggle while reading a book.
I am sorry about the heartbreak and your marriage trouble, and that this also happens to be the time your son is ready to ween, but you can maintain the bond with him, it just grows and changes a little as he grows.
I am the only female in the house with 3 men (my husband and 2 sons) and my #1 rule is that mommy gets as many hugs and kisses as she wants. There were times I had to chase the little ones down to hug and kiss them, but they are getting used to it now, and instead of any protest, they now offer hugs a kisses a lot.
I am sorry for the difficult time you are in now and I hope this helps, if even a little bit.