Oh goodness some of these stories are heartbreaking. I am so sorry for anyone going through this.
MissHL we adopted our son 6 years ago, we have a birth dd who is now a teen. Being a mum, being a mum to an adopted child and to a birth child (on the autistic spectrum) has been incredibly hard at times.
I think sometimes what can happen is difficulties can push people together, or push them apart! My dh can drive me mad sometimes but he is always pretty dependable and the issues we have faced have mostly pushed us together.
I don't know your situation but I would say that this current Covid crisis has made pretty much made everyone's life much harder.
So before making any life changing decisions I would pause for breath.
In general if a partner is abusive or someone does not feel safe etc then of course you must protect yourself. But your situation does not sound like that. It sounds like he has lied and let you down a bit, and is finding all this very challenging, which to be honest I think quite a few people may be doing at this time!
Is it you, or your dh, or both of you who are thinking of ending it?
If one of you wants to make it work, then I'd consider some on line counselling now to help you work together through this time.
If you want to continue parenting your adopted children and pursue the adoption order at this time, I would personally not involved social services in any marital issues you may have. Or at least I would not spell out the full story to them.
These really are unprecedented times and so as parents/as couples/ as professionals everyone is a bit in the dark.
As long as both of you and your children are safe, I would not be alerting anyone outside the family to the situation, except to seek the help of a professional (and qualified) counsellor.
If, in the future you and your husband decide to separate, then you can do so, and work out child care arrangements as any other family would, and pursue divorce as any other couple would.
IMHO if you involve social services now the whole situation may be taken out of your hands.
If at all possible, give your dh some leeway, talk, be open about your feelings but also be generous if you can.
For example:
He may feel pushed out if you and the child are building a bond and he is not (our son took ages to bond with my dh - luckily my dh is not the jealous type and just accepted it!)
He may find parenting more challenging than you/more challenging than he expected, he may need support and help to feel able to cope. he might simply need to meet up with mates and feel like 'himself' again, and of course none of us can do that at this time!
This difficult situation may not always be the case.