I'm going bankrupt on monday, husbands on jsa which I have declared that he contributes half of to household, if i get ipo/ipa and he later gets a new job will I have to declare it and pay more.
yes that's correct. The declaration of other contributions to the household when it relates to your partner's, or spouse's, income should be proportionate to your respective incomes.
So If his net income was £1200 and yours £800 then his income is 60% and yours 40% of the total household income. In this scenario if the OR agreed to a total household expenditure allowance of £1600 then your husbands contribution should be £960 (60% - which should be declared as other contributions) and yours £640 (40%) therefore you personally would have £160 disposable income and as the only bankrupt party would be required to pay 50% of your £160 diposable income into an IPA.
This leaves you £80 for yourself and £240 for your husband as the non bankrupt spouse meaning his position is unaffected by your bankruptcy.