I’m afraid we can’t easily do anything about how key presses are delivered to Dorico via Synergy.
As for the horizontal scrolling direction, this has been pointing out before but we think it’s Cubase that goes the wrong way, not Dorico 
We have talked about adding an option for this but I’m afraid it’s not yet risen to the top of the priority pile.
Yes, I agree that Cubase’s scrolling seems backwards. I will post this on their forum as well. Regarding Synergy, if I use Dorico on the Macbook and have that set to server, and the PC as the client, then it works fine.
Just curious if anyone looked into what caused the crash reports I had posted with the midi issue?
From @Ulf’s previous message in the thread, it seems that the majority of the crashes were in ARIA Player and Kontakt, which means unfortunately we can’t do anything to help – those crashes need to be reported to the teams at Plogue and NI respectively. One crash was in HALion Sonic, and Ulf reported that crash to the HALion team.