UK plab2 visa reapplication [duplicate]

I am a Nigerian doctor working in Saudi Arabia. I am married with 2 children but my family resides in Nigeria. I was denied a plab 2 visa recently (see picture) and I am planning to reapply. I have also been denied 2 years ago for a visit visa due to lack of funds/fund parking. What are changes I could make to improve my chances? By changes I mean:

1 Should I reduce my proposed length of stay to 3 days? This I already plan to do.

2 The only evidence that I have booked for this exam is the confirmation email usually sent after paying. How do I go about getting it certified like the ECO hinted? Should I include other things like a receipt generated from the GMC website? Also include all the email communication I have had with the GMC?

3 I stated I wanted to familiarize myself with the UK healthcare system. This was interpreted by the ECO to mean I wanted to do a clinical attachment. Should I explain this in my cover letter, on the application website or totally ignore it?

4 I applied for a PLAB visa. However I was assessed under the clinical attachment category. Should I point it out or keep quiet?

5 This last application was in Nigeria during my leave, now I plan to apply in Saudi Arabia. Does this affect my outcome positively or otherwise?