"Previously employed in UK" will not make any difference to his application for JSA here. The process is that he presents himdswlef at hios local SW office. THey will ask him to prove his ID, complete an application form for JS (or JSA as you call it), fill another form to process means-test.
The means test will determine his entitlements and will take account of your income (he may be asked how he managed to live without claiming before now!). Separately, he may be asked to prove that he is genuinely seeking work (and this will include lookign for work outside his own field if ther are no jobs available in his area), which is proved by producing letters of rejection from jobs he applied for, names, dates phone numbers of jobs applied for and he will be asked to register with FAS after about four weeks.
All this may sound "hideous" but it is not as bad as it sounds, when dealt with one step at a time. Step one, call to the office....