I'm 5+ years out from d-day, and WS and I also legally separated and lived apart for quite some time. Here's my 2¢. No, the relationship is not the same as it was pre-d-day. That mad, unconditional love feelings have not returned. There are DEFINITELY conditions now. Some days are quite difficult emotionally, because I see my WS for who he really is now, and understand what he is capable of. Do I think he would cheat again after everything we've been though? No. Would I bet my life on it? HELL NO. Do I have a plan B in place for just in case? Yes.
But... most of the time things are pretty good and I recognize the fact that who I though WS was, and what I thought our relationship was pre-d-day wasn't real. I just didn't see the full picture... yet. So, in that regard... I'm happier with life now because my blinders are off, if that makes any sense.
Now, for this part:
I am mid/late 30s and our child is now 6. We always wanted two children but due to the affair and aftermath this hasn’t been a possibility yet. I feel like due to my age I need to decide what I’m doing with my life, am I going to stay with my husband and try to expand our family as we once planned to? But this bad time will be forever physically evident with the age gap between our current and any future child.
If your biological clock is ticking and having another child is very important to you, this would be my pragmatic advice from a non-emotional standpoint.
Could you figure out a way to raise two kids on your own? Can you afford to pay rent/mortgage and childcare on what you make right now?
If yes, then have a second child with your WS and have a plan B set up in case you decide you need to divorce.
And I'm sure some people might this is bonkers, but this is my reasoning:
Your children will be full-siblings, that share the same father, and you can avoid some issues blended families face with coordinating custody schedules or drama with step-parents or step-siblings. If you have a second child solo, or divorce, work on healing, start a new relationship, get married? and then maybe have a second child with someone else, then in theory one of your children would be with you full-time, and the other would be in a shared custody schedule with your WS. If both of your children have the same father, then you would only have to coordinate custody schedules with one person, and your kids would spend holidays together regardless of which parent they're with (if you all didn't spend them together).
If you google statistics, they vary, but generally they say that first marriages are about 40% likely to end in divorce, second marriages are about 60% likely, and that number goes up if the second marriages involve kids from other relationships.
As for the age gap, my kiddos are 7 years apart in age, and it's been way more enjoyable that I worried it might be. My oldest was totally potty trained, could get dressed on their own, get themselves their own snacks if they were hungry, slept through the night, was in school full-time etc., and there was very little jealously around a new baby coming into the house. If they were only 3-4 years apart in age like we had initially tried for, I think it would have been much more difficult helping a preschooler that wouldn't be as independent while also taking care of a newborn. Plus, we only had a couple of years where we were paying for childcare for two kids at the same time. Now I have a kid that's elementary-school aged, and one in high school, so I only have to worry about summer camps or paying a babysitter on days schools are closed for one kid.