I'm surprised that you actually get data on the SBC. Once you do a BaroSensor.begin(), the I2C in the controller switches to master and will not listen to the slave address so 'commands' from the SBC will be ignored. Now you have two masters on the bus. When they both talk at the same time, there is a bus conflict; I2C supports that (one master will win and the other one will give up) and it's called 'lost arbitration' (or something like that). Multimaster is (partially?) supported in the Wire library, it can at least report back that it did loose the arbitration.
One thing that you need to do is after you have received data from the sensor is to switch the I2C to slave again using Wire.begin(slave_address) so it can listen to the SBC. If it will be successful is another question.
You will probably be far better of with a different means of communication with the SBC. Serial communication would be simple. Alternatively, there is a software I2C implementation that might work; that way you can have two separate I2C buses, one for communication the SBC and one for the communication with the sensor. No idea how well the software I2C implementation works.