+ AA6YQ comments below
The antenna selection is indicated in the same query ("I") used to get the frequency and mode. Here is response format,
a = 1-3, indicates antenna selected
b = 0-2, indicates selected bandwidth (0-Wide, 1-Intermediate, 2-Narrow)
d = 0-5, indicates the mode selected
f = 8 digits show transmit and receive frequency
g = 0-2, indicates AGC setting
The meter readings can be obtained with a M command. I tried the command using the Message Monitoring tool. Adding H1 before the meter command and a H0 after. I tried it with M in receive and the S-meter value was returned. I did not try the meter commands in transmit so far.
+ Commander does not display antenna selection for any supported transceiver. For most radios that can switch among multiple antenna connectors, this would be consuming scarce screen real estate to replicate information already displayed on the radio's front panel.
+ In order to display a JST-245's S-meter and a selected transmit meter, Commander will have to know whether the radio is receiving or transmitting, which its currently not the case. I will extend Commander to do this, and send you this extended version to test. Then we can proceed to add support for metering.