You might try packing your boolean bits together into 1 variable and using an enum to keep them straight.
Arduino has bit commands if you don't want to shift and mask.
But doing that does eat cycles, the old memory and time tradeoff.
Keep the buffer for now. It may not be the problem and it serves as a kind of record of operations.
The 1284P has 2 hardware serial ports. Is there any chance that you can use 1 to print a trace on a PC?