Although nothing is a 100% guarantee against punctures, Schwalbe Marathon Plus are certainly the tops for puncture prevention and they are hard wearing. However, as a result of their thick inner layer protection they are a bit more rigid so less comfortable than your standard tyres. Since you are always on tarmac, carrying a substantial weight and have sprung forks and seatpost, I don't think the comfort reduction is a sufficient reason not to fit them.
I've used them on three e-bikes for over six years now and have had one puncture with them in that time, slow enough for me to get home anyway with a re-pump, and that was caused by my foolishly riding over piles of blackthorn cuttings on a cyclepath. Over the same period I've long since lost count of the number of punctures in my trailer wheels, not MP equipped. In another comparison, a Giant Lafree I owned had an MP on the rear only for the last 18 months I had it, during which it suffered four front punctures in it's standard tyre but no rear ones.