I never experienced red dots on any of my limbs after consuming 3-FPM. The most pronounced warning sign, that I was heading towards a serious condition if I continued dosing is that I could feel the pulse in my feet very clearly and that was really annoying, especially at night. Furthermore there were flu like symptoms. So all in all mainly physical side effects, while the mental comedown was very mild.
I can imagine, that if you really exaggerate and consume several grams per 24h (there are many people, that seem to have survived that, but I am not sure, there was one guy who used it as aphrodisiac and then abruptly did not post anymore, see the thread in other drugs, he wrote essays about 3-FPM and could not stop dosing 3-6g per day, pretty scary actually), you could reach a point, where clinical vasculitis sets in like in the article posted above by Shambles.
In my view good 2-FA (if it has to be an RC) is vastly superior to 3-FPM. But good 2-FA is very rare these days so 3-FPM can be an alternative. Street speed is superior to both, whereas the comedown is much more tedious.