What is the maximum allowable distance between a bedroom and bath

I am happy to report that, despite building codes for ALMOST everything imaginable (in the US anyway), this isn't one of them anywhere I know of!
There isn't even a building code for what constitutes a bedroom, although in zoning and real estate tax appraisal, a room cannot be called a bedroom unless it has a window and a closet.

Being an old lady with her own personal plumbing problems, I need to sleep out in the hall outside my bathroom, because I don't have the ever popular 'en suite' bath.

Agreed, there is no max distance, I would have to ask why this is or was an issue?

IRC specifies sizes of rooms. Local codes may be more stringent but there is nothing about distance between rooms. Remember, some old Colonial homes didn't even have bathrooms.

How fast can you run. Likely a code, as well as how many baths for certain amount of Bedrooms. If Not, should be?

If you NEED a bathroom closer to a bedroom then you look for and buy a place or rent a place that has one closer. No place I have ever seen has a bathroom all that far from anything in a house (and few people can afford Mansions and anything else really isn't all that big) or any apartment I have ever rented or visited.