General GRE and Physics GRE are two different preparations, but that doesn't mean you can only prepare for one of them.
Studying on alternate days could be a good method. After all, you won't be fully studying everyday for pGRE in the next five months.
If I were you, I would be more concerned to increase the verbal score. It is a psychological thing, I see scores < 160 all the same, and scores > 160 all the same (except 170). So I will feel adequate if I can get scores above 160 in both. I do not know about how the admission committee thinks about this. My guess is that there'll be a cutoff that you should avoid (exactly where, nobody knows), but you still need to reach a high score to have your GRE score as a strong point (not just a neutral point).