In several different writings, by several authors, I have seen however preceded with a semi colon, but I am unsure if this structure is set in stone (similar to using a comma before "but" and "because"). Following are two of my sentences and I am unsure how to use however correctly.
"Unlike academic achievements however, passion—the drive to improve—is an inherent trait of an individual’s core."
"My income brought stability and positive changes at home; however, my relationship with education has since taken several unexpected turns and has brought many hard lessons."
Your sentences are correctly punctuated.
When 'however' begins a clause, it is preceded by a semicolon or a full stop.
I don't know why you believe that 'using a comma before "but" and "because" is set in stone'. It most certainly is not.