I have read all of your comments op and whether you are "real" or not the fact of the matter is that if you wish to live in accordance with your cultural expectations and have a mortgage, there has to be enough money coming in. That applies to all people whatever culture they are from.
From everything you have written neither you or your husband have particularly marketable commercial skills or experience at present so both your expectations need to be focused on a modest lifestyle and maintaining it. It's a shame that you didn't work for a few years before having children - we have some South Asian neighbours and that's what their female children have done.
Your DH sounds like a feckless lazy bastard but he is right, I think you do need to work particularly as you have married a man who isn't capable of reliably earning a modest living. Sadly, I don't think career changes or retraining will help in light of the underlying attitude.
Whilst I appreciate you have three young dc they are at school and nursery. I have been a SAHM and I don't understand why the domestic load takes you all day. I had two dc and a dh who did none of the domestic load (which was fine because he was workaholic and brought home the bacon). I have honestly never had so much time on my hands as when I was a SAHM and especially when the dc were both at school. We had tidy up time before bathtime (took about 15 minutes), bath, story, quiet time. DH got in at about 9.30 and chatted whilst he ate. I made sure DC's book bags, shoes, kit, etc were ready by the door. The DC and I got up at 6.30/7. Washed hands and faces, dressed, breakfast of toast/fruit/Yoghurt took about 10 minutes, hands, faces again and teeth. Then they watched TV or read whilst I tidied the kitchen, did the dishwasher, hung a load of washing. Left for school at 8.30, back by 8.55. I probably spent about 45 minutes a day on housework and our house was immaculate and large.
Left for school at 3.25, although probably twice a week I had until 4.45 if one was having tea out and one doing an after school activity. Tea at 6ish, proper cooked meals, spag bol, cottage pie, fish fillets, etc, with veg and or salad bits, reading, music practice, bath at about 7.30, quiet hour, bed at 9/9.30 they stayed up to see daddy - mine didn't need very much sleep.
I can't really work out why you are so full on. I went back to work when I found myself damp wiping the stainless steel kitchen stuff with a soft cloth and baby oil to make sure it was mark free and wishing the cooker could chat.
The issue is your lack of experience. In towns at present there is tons of work and a shortage of people to do it. To start you could pick up work in hospitality/chambermaiding, McDonalds, care work, retail, etc. To move into something office based you probably need to get yourself fully up to speed with Microsoft Office. If you have a legal qual, could you contact some local firms to see if they have any part-time admin roles or need help with transcribing tapes that you could do at home?
Ultimately, if your DH can't or won't bring home enough and you want to keep the house, you will have to make up the short-fall whether that's part of your culture or not or whether you like it or not. Personally, I'd focus on keeping the house and getting rid of the husband but if the latter isn't possible then I'd make myself self-sufficient but if he needs a financially productive wife, he needs to park some of his cultural expectations and take on some of the domestic load. He's living in 21st Century Britain and needs to adjust some of his expectations to suit how and where circumstances are rather than what he'd ideally like. And bring your sons up to share the load and graft.