Congrats for breaking out of the mold and taking it upon yourself to adapt a recipe to your own preferences! I always love it when readers, and my own winemaking buddies, take what they know or have done, and give it a good tweak. Pyment, or a fermented beverage made with both grape sugars and honey, is a tipple that’s not only tasty but one that’s often easier to make than a straight-up mead because the grape juice or concentrate provides additional micronutrients to yeast as well as additional tannin, flavors and aromas. For your calculations, grape juice concentrate sold via home winemaking supply houses, as well as commercially to big wineries (who use it sometimes to make up sugar in low-brix years) is standardized at 68 °Brix, or 1.3421 specific gravity.
You can certainly toss grape skins (marc or pomace) into your pyment to add even more red wine character like you say, but you could also buy some powdered grape tannin, use oak chips, or even use a cup of strong black tea to add some tannin backbone to the wine if it’d be tough for you to obtain grape skins. You could simply incorporate fresh red grapes as well, if you’ve got a source for them. For a dry red table wine style, be sure to start with an original must of at least 22 °Brix (1.092) in order to achieve 12.5 to 13% alcohol (exact conversion depends on yeast strain and fermentation rate). Much lighter and you won’t achieve that rich red wine style you appear to be looking for.