GTMETRIX & other similar reports

Hi Guys, I need to get some correct information in regards to some problems with my websites.

I run a GTMETRIX on my websites, and if I do one per day, no matter what we do to the site, the score keeps changing and usually for the worst. WHY would this happen, does my web guy not know how to make my website appealable for google to not give it a bad score.?

Is there a proper report to run to see whats wrong with your website, and fix it so the score stays high. I mean how can a site drop from supposedly 70% to 41% in one day???
Trying to get my site working fine for mobile and google is driving me crazy, and I have experts working on it, so need to know if my experts are not looking after my sites properly.

2. I have about 100 websites that seem to get a LOT of spam through the contact list... does this happen to everybody or is it just me once again.... through malware, or someones computer maybe not being safe. same emails through all the contact lists? Driving me insane as well.

3. What is the best program to test your site for mobile affectiveness on googles eyes, how would you test it and find what needs fixing? I know the online mobile viewing programs, but this is for google and being great for google searches online

thanks in advance