Being married to Aela is great but sometimes she does get in the way. Will she remain as my mate if I tell her we must part ways? Will this then allow me to get another follower? Thanks.

She will return to Jarvaskr(sp) or your home if you moved her there after marriage. She's been staying in Riftin for me cause she's in the way and I've used followers since. Still married.

Yeah i think you will be her husband even if you don't travel with her anymore.

This^^
If you have moved her to your home she will be there, other wise she will return to Jorrvaskr. No issues with taking another companion, Aela will stay home and cook for ya, and will have a little shop going as well which you receive half of the profits
I recommend taking Janessa as a companion, she takes orders well, she's good with a bow and a sword, she's rather quiet compared to other companions, and from personal experience she's pretty good at staying out of the way as well