Thanks Vic for asking this question. Deciding on what name to use for early generations can be difficult to decide.
One of the problems with the Wikitree policy of 'using their naming conventions not ours' for this time period, is that 1) names are usually in Latin, and 2) there is very little consistency about how they are spelled from one document to the next.
The other issue is that we don't apply the policy evenly, we seem quite happy to use the Latin Moravia as the Last Name at Birth (LNAB) but use the modern name for the first name - William, instead of Willelmo or Willelmus; Walter instead of Walteri etc.
According to The Scot's Peerage, volume 8 (see here https://archive.org/stream/scotspeeragefoun08paul#page/320/mode/2up
) it looks like the early generations of the family used son of Freskin, or even just 'Freskin' as their last name and it wasn't until 1200 that one member of the family started using 'de Moravia' but this name was used by anyone from Moray.
The Complete Peerage, 2nd ed., vol 12, part 1, refers to William, the 1st Earl of Sutherland as using the last name Moray, (or de Moravia) then Sutherland, he signed documents as William de Moravia in 1226 and 1229 and then in 1232 as William of Sutherland. According to The Complete Peerage all the following generations used the surname Sutherland.
I think that the best idea might be to change the earlier generations to Moray, but start using Sutherland much earlier.
Lastly there seem to be many errors in this line, and it actually gets quite confusing as to who is meant to be who. Rather than suggesting lots of merges, I would be progressing very slowly, getting the earliest members in the line 'right' first with good sources and then moving on to later generations.