I agree that it's a bit too much citrus. I really want the allspice to be the hero of the drink, rather than an afterthought. Might try simply reducing the lime to 1/4 at first.
This has a very "fall season" cocktail feel to it. Allspice, cloves, cinnamon from the homemade Allspice dram plus the nutmeg. I could see where this would make a great "Hot Toddy" as mentioned.
I am a big rum drinker, that this is an outstanding mix of Caribbean flavours. Everything is well balanced. You can taste the Pimento Dram and nutmeg. Not too sweet as some rum drinks can become.