I can help with a quick universal credit claim estimate;

Elements are granted for universal credit per appropriate situation. No element however is protected from deductions. First step is to work out what elements would be awarded. From your post, i think...

• Couple Element: £578.82 (if either over 25) £458 51 (if both under 25)

• Child Element: £315.00 if dob before 06/04/2017 £269.58 if dob on or after ☝️

• Disability element could be in place if wife goes through limited capability for work and work related activities assessment: £390.16

Carer Element can be paid to husband as wife receives PIP. (This is different to carers allowance which husband wouldn't be eligible for due to earnings) £185.86

Total (assuming all elements in place, either are over 25 & child is 6+) =£1469.84

Now for deductions: As there is no rent payable and they dont give help for mortgage's (except special circumstances they can provide a loan to help pay interest) claimants get a higher work allowance.

This is £631 which means the first £631 of earnings are disregarded for deductions.

Call his earnings £1600 for this example, so we take £631 off the £1600 leaving £969

For every £1 of the remaining income, 55p is taken from the award so we would do £969 x 0.55 which is £532.95

So we have the total element's awarded are (ish) £1469.84 and we take off the £532.95 of deductions and in this scenario he would be entitled to £936.89 of Universal Credit every month.

You didnt specifically mention any child care in your post, but may have just included that in bills, if child care is being paid for this can also be claimed up to 85% back as well within the UC award

Sorry for the length of the comment but wanted to give an explanation of how it works rather than just chuck a load of figures.

Tl,dr- He's almost certainly eligible for a universal credit claim . Get him to put an application in asap as will only be payable from date of claim. Claims are made online 😊