Awright, back to basics: did the critter have spots lighter than the background, or darker?
Light spots on dark background = char.
Dark spots on light background = trout.
Now, light and dark can vary, as can coloration due to any number of factors cited above. Brookies and browns will both have red spots, but different kinds and brookies' have a blue halo. But brookies, browns and their hybrid tigers have square tails and we have a report of a distinctly forked tail. The bull trout hypothesis is rejected for being outlandish (fisheries managers these days are more sensitive than they used to be to the ecological appropriateness of species to regions; I can't believe anyone would have stocked one in a Cape Cod kettlehole on a whim).
So, with a forked tail and any plausibility of being here you've got two choices: landlocked salmon (trout*) or lake trout (char). So it all comes down to the spots.
[*not really a trout, of course, but meets the "dark spots" criterion]
Now, my guess is that you've played with this fish in your mind too many times and can no longer tell whether it was dimpled or pregnant or dangling, but if you can answer the spots question I believe you've answered the ID question.