carer payment is a better payment to recieve as there are two parts.
One is $500 and the other $150 So its 650 a f/t and you still get FTB a and B

Your hubby can get carers too if he is providing care for your son. (If i read right)
This will increase your overall amount per f/t

Dont stress about the forms. Just take them to his dr and then answer the q's you need to answer after the dr. that way it will be easier for you and whilst it can take a while to get processed it is well worth it for the extra money every f/t and you will get backpaid from the date you hand in the forms so go the the dr asap

Goodluck