I’m late to this and I should have spoken up earlier.  Cos… I’ve had my door handles on and off a lot while developing my machined handle replacement.

I only use the big screw in that handle. The smaller outboard screws eliminated.

The big screw, I’ll give you it in inch measure:

It’s a pan head,, Phillips drive, full length thread
Head diameter  0.484”
Overall length 1.434”
Length below head 1.255
Threaded major diameter 0.241”
Minor diameter ( rough) 0.188”

Hope this helps at hardware store

Alistair