APROO Strap change help

[RRM1020]

Hello all,
I need some help.
I have an APROO Grey Themes Titanium on a bracelet. Just love it.

While at the boutique I picked up a rubber and a grey horn back straps for it.
I am afraid of changing straps bc my tools won't budge the screws and I don't want to strip them.
I even tried putting heat w hairdryer I loosen lock tight. But nothing.

What tools and method do I need bc I want to change the look.

Thanks,
Roger