TPS65235: DiSEqC 2.x recieving back messages issue

Could you help me to clarify for my friend the application of TPS65235 with DiseqC 2.x support? In our circuit the 22kHz for transmitting (22 kHz TX) is generated internally. The 22kHz detector needed for receiving return messages (22 kHz RX) is external (in other IC in the design). The issue is that there is unable to receive DiseqC return messages. The circuit schematic was double checked to be correct. My friend keep to wrong blame the bypass MOSFET. His testing methods are leading him to wrong conclusions. Please clarify:
1. Could you tell which type of bypass MOSFET is needed for 15 Ohm impedancy bypass? N-type or P-type? Which one is correct? For which one type of MOSFET is designed the TPS65235 pin GDR gate driver ? Will the use of a transistor with opposite (complementary) type give the intended way of work?
2. Could you confirm the way of work of DiSEqC 2.x. For receiving DiSEQc 2.x return messages, the bypass MOSFET must be blocked (to get 15 Ohm output impedance at 22 kHz, to allow return signal to pass through) , and for transmitting the 22kHz the bypass MOSFET should be conducting (to get low 22kHz output impedance).
3. Could you confirm that to allow paragraph 2, the TPS65235 Control Register 2 bit 1: TONE_AUTO must be set to 1. Without this the bypass MOSFET will be always conducting, and  the 15 Ohm impedance needed to receive 22kHz from ODU is not in force. With the bypass MOSFET conducting there is not possible to receive DiSEQC back messages reliably.  
4. Could you confirm that with wrong MOSFET type, transmitting and receiving of back messages is somehow possible anyway, but circuit application is all wrong.