I would imagine that if you were only eating 1 meal a day that you are likely not getting enough calories (which can also effect your levels). How much protein is in 5 scoops of your formula? My daughter is 9 and has CPKU. At one point we had a very difficult time getting her levels low. We kept decreasing her phe intake, but the levels did not budge. In the end, it was that she was not getting enough calories from food or protein from her drink. We ended up increasing her medical drink (she is at 70 gm protein a day right now from her formula) and increasing calories (and phe) through food. Do you keep diet records before going to the clinic? If so, the dietician should be able to see if you are getting enough calories. You can also get a full amino acid profile and that can tell the dietcian and doctor if you are getting enough or if your body is catabolic (breaking down muscle to get calories and protein).
If your tolerance is 325 mg, there are lots of resources now for good low protein recipes. You should not spend your day hungry and miserable. Cook for Love (my site) has lots of recipes and no fees, Cambrooke has tons for their products, and Amanda Cosbourn (a young lady from Canada with PKU) recently launched a website where people can post recipes.