Hi Buckle
I think it is fairly common for CGs in recovery go through patches of being fed up with others who appear not to want to change or won’t change BUT I hope he doesn’t abandon his GA group altogether.   I have heard many CGs say this and ‘some’ have come of the rails later as a result of not having that solid base to re-affirm their determination. Keep a beady eye on him and perhaps suggest he does a couple of night between now and May or perhaps posts to Gamcare – he can do that anytime. 
I found it really hard to think that my CG had to go the rest of his life tuning into his recovery support every week but it isn’t really that tough.   Having been through rehab he doesn’t go to GA regularly but he does use support often.  F&F can and should move on once recovery is under the proverbial belt but F&F do not own an addiction – it is not the same for the CG.   Colin in Brum’s thread ‘Anniversary’ that has been brought up to the top of My Journal recently is a good reminder, if one is needed, that the CG recovery ***** constant overhaul and re-affirmation.  
I have worked out that 100k must be about 60 miles as my favourite running distance is 10k so I know that is 6 miles. 60 miles is a heck of a distance.   I have only ever managed 30 miles in one day although there was a bit of climbing involved.   I wish you both well. 
I am sorry to hear about his mum but glad that you are getting your man back more.
speak soon