Who to 6 star next to improve DB10 runs and team suggestions

I'm currently running Vero (L), Spectra, Megan, Chasun and Bella right > boss, as it's the only team I found to be able to have a chance of succeeding after a lot of experimenting. But the problem being is that team only has around a 65%ish success rate. With a 70% in the Zaiross stage depending on the crystals armor break.

So I need help choosing which monster to 6 star (my top options being megan or bernard from looking at others' teams) or swap in for my team and maybe some rune checks if they're on par for the requirements for DB10.

https://swarfarm.com/profile/lebondage/