Hello. In contrast to the RX/TX lines, the wireless_serial app's USB interface (provided by the usb_cdc_acm library) and the radio interface (provided by the radio_link) library both have flow control and buffers built in, so there should not be a problem with sending data too fast through those interfaces.
You said that your Java client app stops sending the data. You might have experienced a situation where the Wixel's USB receive buffers got filled up, so the USB virtual COM port TX buffers on the computer filled up, so that all writes to the COM port had to block indefinitely. I don't know what would the root cause was though. The Wixel's wireless_serial app is supposed to be reliable and if there is some bug in it then we want to fix it. It would be very useful if you could make the bug happen faster, then reduce the system to the simplest possible system that reproduces the bug, and describe the situation in detail to us.
The three main libraries for writing a wireless app with the Wixel are radio_link, radio_com, and radio_queue. All of those use the CRC feature of the CC2511's radio, so you should not receive bad data.