# 2 . water pump switch is in the best location .
What you need is what is called a 3-way circuit and those switches are only available as a 120V switch in an RV appearance .
Although there are some DPDT switches available I would Use what is installed now .
The bathroom is the best spot for the switch.
# 3 . GFCI receptacle has terminals in the back to add another 120V receptacle that is GFCI protected by the host GFCI.
You could run your 12 guage grounded Romex from the current GFCI to add another receptacle .
You use what is called a " cut-in-box " to house the additional receptacle .
This means you cut your cabinet to EXACTLY fit a " cut-in-box " using access from the front of the cabinet .
Craftsmanship is required .
Make sure that all wiring connections or TIGHT .
Loose connections are what causes fire .