to my knowledge, such a site does not exist (although i wish that it did). for first halves, it's pretty simple, esp with totals.
totals, divide game total by 1/2, then subtract 5 for 1H total. 1H total is pretty much always within a half-point or a point of that. and add 5 for 2H total (ie, 2H total is generally 1H total + 10), although that's sometimes adjusted if the 1H is really high-scoring or low-scoring.
for spreads, divide by 1/2, but there's more variance there, particularly with big faves. a team that is -16 for the game could be -9 or -10 1H, -8' or -9 is most likely.