The SIP provider mentioned their "new" system does require "From" information in header, and mentioned there is no other option for this.
Rather, they suggested provision of service over Static IP, which we will try. (I will keep you posted if there is any issues)
And for the "HPET" message, we were surprised because running "HPETTool64.exe /t" command returned "HPET is supported and enabled..." message earlier. I ran the suggested command and it looks good now.