IIRC Ronnie O'Sullivan runs for Woodford Green so you could look in his bio (which is pretty running heavy for a snooker bio!) to see what he says about them(!). He's a bit faster than you but not shedloads.
And I have done marathons on scrappy training (not quite that scrappy though) before so I do have some idea what I'm talking about here! Better training = happier last few miles = all round positive experience.
My OH used to train for HMs on 2 runs a week and no footie; but he did find the running much easier when he moved up to 4!
I reckon if he conscientiously always always did both runs, and if the midweek run was half the length of the long run, and the long run went up to at least one 20 miler, he might be OK (though it really is cutting it fine).
yes he should start running now - it will much reduce the chance of injury if he gets some basic training in now (say 10 miles a week).