It looks like you have a great plan!! I have read that neutering may help with marking in some instances but I think it will be more dependent on your training techniques. I have heard, from a vet tech, that it is helpful to neuter before they hit puberty (not sure what else to call it?). I am sure it must help in some way even Marley is a bit older.
I think your plan looks perfect and whether you decide to neuter or not, Marley will be potty trained in no time. Good luck!
