Very nice! 
I’m sorry to hear that. I hope Mac users here are able to help you. I’m a PC user, and I haven’t ever made cover videos yet. I’ve edited other kinds of videos before with Adobe Premier Pro, but it possibly wouldn’t run on your computer. Some people use DaVinci Resolve, but it might need more processing power.
There’s a thread about making cover videos and editing them. You might like to check it out: Pam and John's "How To Record Yourself" Parts 1 & 2 (Audio & Video)
But hopefully Mac users here are able to help you. But it is quite possible you might need a new computer.
Best of luck, and I hope you can find help and a solution.