CC1352P: 2W power amp with CC1352P - FCC requirements ISM

I believe we haven't tested this. I would suggest getting one CC1352 Launchpad and an evaluation board with the PA you want to use, connect those two together and do some measurements. 

Why CC1352P? Most front ends have high gain, do you need more than ~12 dBm in on the 2 W amplifier? 

My question pertains to FCC limits, not hardware implementation.  Figure 1 in the following article seems to suggest that the FCC will allow up to +36dBm at 915MHz as long as FHSS with 50-channels or DSSS is used :

Elsewhere, I read that the FCC limit is +30dBm and the only way you can "add power" is by adding a higher-gain antenna.  Is it possible that I can use a 2W (+33dBm) power amp with the CC1352P as long as I use an antenna with a gain that is less than 3dBi and still comply with FCC regulations ?

See https://www.ecfr.gov/cgi-bin/text-idx?SID=34582d34516b13798d658b3323cd6035&mc=true&node=se47.1.15_1247&rgn=div8 for the official text. 

The way I read this is that the limit is 30 dBm conducted given that the antenna has a gain of 6 dBi or lower. 

Since "The minimum 6 dB bandwidth shall be at least 500 kHz" is an additional FCC requirement, are the four WB-DSSS modes listed below the only modes that can operate at 1W at 915Mhz when using the CC1352P ? 

No. Please read 15.247 which I linked to. If frequency hopping is used, 500 kHz BW is not a requirement. 

Unless I missed it, I only see DSSS (direct sequence) in the CC1352P datasheet .  Is the CC1352P capable of FHSS (frequency-hopping) ?

Yes. One example, see the TI 15.4 stack.