I think you’re wanting validation that because he backed out of the meet up that it’s all ok
It isn’t; he took drugs in a house with 4 kids.
You aren’t married so don’t have a strong case for getting financial support post separation.
I suppose it depends on how much you financially depend on him.
You will likely qualify for social housing with 4 kids and you will get benefits as a single mum. More so if you are disabled or any of DC are (in case you aren’t working due to either of those things??). If any of those apply and you do not have PIP/DLA then please fill in the forms (google how to fill in pip form, disability charities have advice), as having the entitlement means you get more UC etc. You must phone UC within 30 days of DLA/PIP award to have UC backdated to the same time.
What I would advise you do is look at turn2us benefits calculator and put in a couple of scenarios - you as you are with him, you with kids not working, you with kids working part time, you with kids working full time. Keep putting in figures until you find something you could live with.
If he’s bringing in £100,000s and you’re living a champagne lifestyle with designer cars, bags and holidays then you just might have to suffer it if you want to keep that.
But I suspect he is Joe Bloggs bringing in average to good wage so you will probably be financially better off or comparable without him provided he pays child maintenance.