Will increasing my internet speed in my plan fix my frequent ping spikes? in a house of 6 that uses 10 devices sometimes.?

Depends on the bigger picture. You will definitely have issues if you are not using a router rated AC1900 or higher.   Older wifi extenders will also cause issues, you need to use a mesh system.  Otherwise it depends on what speed you currently have.

depends on if the providers line actually 'can' increase your speed .. thats iffy sometimes .. it should help out alot with that much usage, i'd try it, and if its not doing anything i'd call them right back up and trim the plan down again ..