Here's my blunt opinion.
Your husband seems to be multiplying wives for the sake of it. He shouldn't be flirting with other women and trying to get another wife while he has 1 not living with you (I understand that situation), and 2 overseas. He needs to slow down and concentrate on what he's got, focus on YHWH, pray for wisdom, and have patience.
Ok, now that's done with, dealing with flirting. You know I've never really had to deal with that, it hasn't been a thing that's happened here. If it's upsetting you, then say something. Maybe it's something he needs to slow down on until you get your head wrapped around it. What situations is he flirting in? Are you there at the time? Do you need to remove yourself from the situation and go and pray for a while or take some big breaths? Maybe go for a walk.
As for numbers, well we have decided not to have a certain number of children but to leave that up to YHWH. It does make it difficult sometimes, because we can't plan very well for the future without knowing what vehicles we will need, how many bedrooms etc. But we're relying on YHWH, and we're completely focusing on Him. So when I start freaking out I need to remind myself to calm down and that YHWH has this all planned perfectly.
One time when I was freaking out about this He gave me a dream. In my dream there was chaos, lots of things happening, but then I saw YHWH's hand in all of it, and I realised that it was His plan and it had to be like this to get where He wanted us to be. For example, I was pregnant with quintuplets in my dream, and I saw that not only were those children a wonderful blessing, but through that pregnancy we got a larger house, and had I not had that many children we wouldn't have been able to get the house we desperately needed. There were many things like that.
So, keep focusing on YHWH, knowing that He has a plan for your life. We never know what's around the corner, numbers or not, wives or not, children or not. We have to hold on to Him through the craziness.