He sounds depressed too, actually.
I know (in our x-post) you say he doesn't want to be in work, but many men are of the view that if they're not working they are worthless. It sounds like he's covering up perhaps his embarrassment, and shame of not working.
It also sounds like he's projecting his frustrations onto you.
It was him telling you that it would be difficult to cover childcare costs- not you that pooh-poohed the idea!
If ds is 2.9, very soon you're going to be eligible for the nursery grant, which iirc covers 15 hours per week at a local nursery.
Obviously, I don't know how far away that would be (are you urban or rural?) but it would be a good start in terms of covering your part-time work.
If DH has worked in an office in public service (local govt?) then he must have IT skills such as excel, word, access maybe. Presumably customer care skills, etc etc, which are transferrable.
Please don't mind my asking, but is he much older than you are?
The B&B thing sounds like a good idea- and its very easy to stop if you both decide its not for you, as you're not having any alterations etc to provide it. Would this be instead or as well as visiting students?
If it's 'as well as' then I would think it is time to suggest to him that you downsize your house!
2 adults and a toddler do not need a 4 bedroomed house, and it must be eating up money heating, and lighting it.
There are some really good threads on mn about making your money go further, and there are lots of ideas on them about where cuts can be made/savings shaved etc.
Aside from the view you have of yourself, which I am sure is not a true picture (!) these would be practical, small, achieveable steps you could take as a family, which would demonstrate to DH and parents how mature and adult you are.
Just don't bite off more than you can chew!
FWIW I have been at the bottom of that pit. ANd it really does seem as if it can never get better.
But it does, truly.
HTH