Let me see if I understand this correctly. Your local won't let you bet full game sides or totals until game day, but he will let you bet first half sides and totals several days before the game? If I have this right, this is a situation that I can't imagine having a happy ending. Clearly this is an oversight on his part. I don't know enough to guess at what the result will be, but I recommend spending some energy thinking about how this might end before going too far down this road.
Generally, if you like a side or total, the 1H play on the same side or total is going to be a good play. There are two exceptions: One is when the 1H number ends up being key. For example, if you like over 43 for the game, if there's a 21.5 for the first half you might want to reconsider betting that one over. The 21 in the 1H will be much more key than 43 for the game.
The second situation is if there's some aspect to the games or teams that would make you think that 1H vs. 2H performance might be skewed. For example, If I liked a team for the game who was traveling east for an early start, I might hesitate to bet them in the first half if I think they'll be stronger for the portion of the game that occurs later.
