The EDS is mostly a possible connection if there is family involvement. Mostly something to consider if there is family history of joint complications. I strongly suspect it with my mom's side of our family, but nobody in our family is diagnosed. Worth looking into if you feel like you fit, but it's one of those things that might or might not be present. (Though if present it would *heavily* reinforce a case for MCAS.)
Re: dermatographia. On page 10 of that 77 page document it lists the way dermatographia tends to present in MCAS patients:
Another very common dermatologic finding in MCAS patients is dermatographism. [48]
Sometimes simple removal of clothing makes it apparent, but integrating a simple light
scratch test into the physician’s standard physical exam is an easy thing to do. The
dermatographism of MCAS rarely is so vigorous as to manifest hives; instead, usually only
erythroderma is seen in the track of the scratch, arising within 1-30 seconds and often
persisting in full splendor for 5, 10, or even 15 minutes or longer.
Your description fits that easily. It's a mild form of dermatographia, but the mild form is what's common with MCAS. (Though far from universal). Also, this is the same way my own skin responds. Including cuts and especially scrapes. Just red marks, but rarely raised hives. (Though occasionally mine do the hive thing, but usually just when something breaks my skin). Mine itch, but then I itch all the time and at the slightest provocation.