Dragino LSN-50 AT+TDC clarification & soil moisture sensor

Dear All
Good day

I purchased the Dragino LSN-50 recently to make a simple Soil moisture sensor. I want to take the readings and transmit every 2 hours (since no significant differences will occur sooner). Is the AT+TDC command that configures that? I saw from documentation that default is 30.000ms (30 seconds).

also is it possible to change the transmit time over the air? in documentatiosn says that by sending a down-link packet with payload for example 01 00 00 1E changes TDC to 30sec but didn’t work when I tried that.

I figured out how to connect a soil moisture sensor but i want your opinion if this is ok or if I will have future problems (battery drain etc…)
To get the reading of the soil moisture sensor I connected the Sparkfun Soil sensor the sig pin, (this is the sensor https://www.sparkfun.com/products/13322) on the ADC measurement pin PA0 and the vcc and gnd on the vcc and ground pins of the sensor. To calibrate the sensor i sank it till abt 3/4 in the water and saw that the reading was abt 3V. So i configured in Cayenne to show as gauge meter with range 0-3V. (0 means dry and 3V means max wet)

Is this a good implementation?

Thanks in advance!