I suggest you start avoiding SHJ. The 2-year road closure will make getting to Sharjah one hell of an experience, and the ticket isn't that cheap anyway. I suggest you buy the comfort of your mind and avoid G9.
No reason to use your miles for the trip unless you need they're expiring and you need to burn them. But paying AED 3,300 when you can pay much less is just too much.
Since you're arriving at 0540, I'd consider either GF or J9. They have good timings (although you'll bear the full brunt of DXB crowding during your layover). I believe you'll be getting the A340 on GF (which has personal IFE in Y) which never fails to be fun.