If you need to split chain on a regular basis take off a link and replace with a split link .... you can even get split links that require no tools at all to fit. lots of multi tools come with chain splitters.
Your physio needs to find another job. If I was to advise you at all I'd say cut out the football. I've known so many pals to have problems later from their football days. Never played football but ran my 1st marathon in 1981 (3:23), my 4th Marathon in Sepember 2002 and ran my 35th in October 2006 (3:26). Have done as many as 10 in one year (6 in 2 months) and never been injured training or otherwise. Probably do 6 marathons next year and dispite being 26 years older I am confident of getting the elusive 3.15. As said before gentle increases in miles to get your body used to the distance is probably good advice.