If you send, using the Serial Monitor, "SR410#", then in DeviceRemote(), you are setting Ch, Sk, and Vl to '4', '1', and '0', which, of course, are not the same as 4, 1, and 0.
The mySwitch.switchOff() has two overloads - one takes a string and an int and the other takes two ints. You are calling the two int version, but the data that is in those two ints is not what you think it is.
Try:
int Ch = inputString[2] - '0'; //Channel
int Sk = inputString[3] - '0'; //Socket
int Vl = inputString[4] - '0'; //Value 0 or 1
so that, given "SR410", Chm Sk, and Vl end up containing 4. 1. and 0, respectively.