Has he obtained a record of all his contributions from SW. If not he (probably you) can complete the request form on line. There may be some contributions paid before the self employed days.
Were there no class S contributions made while he was self employed.
Are you saying he will be 65 next year. If so he should sign on for JB if he would like to work for another year or credits to improve his pension.
It is unlikely he would be eligible for any pension at 65 due to the shortage of contributions, so he should apply prior to his 66th birthday.
With 15 years of PAYE he should be eligible for a 75% pension which currently is E172.70.
Finally has he ever worked in the UK or elsewhere abroad