If there is a short fall then clearly the personal spending is too much. If his earnings are low then they are low, I think the promises to retrain etc are a separate issue. You need a plan for how to divide the money you have now.
Would he sit down and look at it with you?
We have a spreadsheet on the computer with ours which is great as we put teh sums in so if we change teh amount put in a column it recalculates.
We have a column with all the monthly income (salary, child benefit, tax credits), one with all the outgoings which can't really be changed (car tax, MOT, service broken divided up monthly, council tax, mortgage, petrol, electric, water, food). Then we see what is left over. Out of what is left over some goes into savings, we each have a personal allowance, mine is more than his as I am SAHM and so do the shopping for dcs, presents for birthday parties and so on and if we can we put a little into a holiday pot or a home improvement pot.
It means that you can open the spreadsheet any time you want and fiddle things around if you need to and it will automatically readjust the totals, then you can look at your bank statement alongside and see that if you have £500 in the savings account then £400 of that is not to be touched but actually £100 if for the new car/holiday/redecorating and you can feel as though you are getting somewhere towards your goal. If there isn't as much in the bank as there should be you can more easily see wha tis not adding up.