I have not had much practice recently with wings and pixhawk, and I dont know the default UART3 baud rate (should be 115200), but you can set the GPS protocol to be auto, and it should detect it automatically. Otherwise you can change the buad rate manually via the full parameters list. One thing to double check though is the connection so TX goes to RX on the board, and vice versa…
As for the servos, what are your arm switch settings, as maybe it is disabling servo outputs until you arm. Otherwise you can try to try servo pass-through just to verify the outputs are working on your pixhawk.
However, in my experience when you get stuck like this, its usually best to just to a factory reset and start again, as from time to time a strange setting is saved on the EEPROM and given the vast amount of parameters you can set, it will be faster to start again rather than going through them all one by one.
If you still get stuck, let me know and I can look into this abit more for you