It looks like you are using the code from the “Example serial code for Linux and macOS in C” section of the Tic’s user’s guide, and you have changed
/dev/rfcomm0 while leaving everything else the same.
Since sending commands to the Tic is working but receiving responses is not working, I recommend that you carefully check the connections between the Tic’s TX line and the HC-05’s RX line. Please post some photographs of your connections here so we can check them too.
Another thing to try would be to increase the serial receive timeout. There is a line of the code that sets
options.c_cc[VTIME] to 1, which means 100 ms. Maybe your Bluetooth system needs more time than that to deliver the serial command and its response. You could try changing that to a larger number like 50 (5000 ms).
By the way, if you don’t need to read data from the Tic in your final application, you could just disconnect the Tic’s TX line and use the system as is.