IP3 can easily be much more that 10 dB higher that P1dB point. You may check for example RFMD amplifiers, there are some with 18 or even 19dB difference.
If you need CATV amplifier you may use BPF540 single transistor amplifier and get your spec. If price is not a main concern use gain blocks from RFMD, Minicircuits, WJ and other vendors. You may get ready to go amplifier with internal biasing and matching for 75 Ohm, stable and with layout.
Darlington is not good for LNA and for high linearity as well.