Hi Michael
Good for you mate.
You seem to be doing extremely well.
In answer to your questions,
1) no don't use your running shoes for the gym work, you should really only run in them otherwise you can put stresses on them that they are not used to, or built to handle. The running shoes will also be more expensive than the X trainers - so even more reason not to wear them out by X training in them.
2)No advice of fitting rugby in with running but certainly by doing more than one sport you will have a more rounded fitness - which in turn will make you less likely to break down with injury.
Good luck and regards