Your husband should have signed for "Homemakers credits" when he first became a homemaker. However that's water under the bridge now.
The first thing he needs to do is to request a Statement of PRSI contributions. He can apply on line welfare.ie. This will show how many contributions he has made since he first started work in Ireland, and also how many contributions are required to obtain the various rates of pension.
He may have enough payments to get a part pension at age 67 and hopefully he will be able to get back to work. This is the only he can increase his rate of pension.
His other option may be to become a Dependent Adult of your Pension, but no one can predict at this stage how pensions will be assessed in 15 or more years time