As your husband has not yet received a decision you would need to enter his current visa details on the application and advise that his ILR application is still under consideration. This means that you will only be charged a small amount of IHS.
Once the application has been passed to the relevant department and your husbands ILR has been granted you will be requested to pay the additional IHS. Your visa will be granted for 3 years so £600 IHS will need to be paid.
Due to the fact your husband is applying for ILR he would technically no longer be sponsored by his employer and therefore you would need to evidence that you meet the maintenance requirements either through your own funds or your husbands.
These funds must have been held for a minimum of 90 days and must be dated no more than 31 days for the date of the application being submitted.