heres the thing a 600pounds short annually looks quite big , its quite tricky but when you divide the required annual gross income and your husband gross income by 12months
18,600 / 12= 1550
18,000/12 = 1500
the difference is only 50 pounds short monthly
this is just a very small amount, so you can point out that a 50pounds short monthly doesnt make you and your husband a burden to the government plus he has overtime and bonuses.