Here are my files for my little RS232 RF bridge boards I made using Flowcode 5.
I also had problems but in the end had very repeatable and reliable comms. Mainly down to getting the correct TX and RX settings.
I see you're using microsecond delays to calculate timeout. Aren't they become invalid or converted to ms if I use 8mhz chip speed (I see, you use 49mhz)?
The warnings your getting are simply saying the delay resolution you can have is 2us instead of 1us and there is an additional overhead of 4.5us when calling the delay function.