Try turning your amps master all the way up and use the power amp side of your amp more then your pre amp. Its hard to sound like Joe in some cases because Joe uses multiple amps. Drop the Digitech altogether because it is limiting your guitar signal to your amp because it too has a master volume. If you do need effects you can try to use it but I really think the SG and straight into the amp will get you closer to his tone then anything else you've got from your discription.
If you listen to Joes solo stuff he's got tons of high cost gear, but if you look at how simiple of a rig he brings with him as a guest its really just him a les paul, an amp and maybe even a boost pedal or something. For example a few years back Joe was in Paris playing a set with his girlfriend. He was playing his newer Bonaburst a boss blues driver and a Hot rod deluxe amp. Everyone on the board was saying "Joe your tones awesome what did you do to get that sound?" and he replied on here it was his girlfriends amp his les paul and a boss blues driver level was all the way up, drive was all the way up, and tone was turned all the way down! It sounded like Joe and other then his guitar he had $700 worth of equipment bought new.
So to sum up what everyone is saying on here its wonderful to try to copy joes tone but remember that phrasing is the key and the only way to get joes tone down is to phrase like joe. The only way to do that is Practice. More then Practice then you ever really wanted. Remember the people who are famous for playing guitar didn't just luck out and get famous they did what they could to get where they are. Joe said in a video once he practices like 6 hours a day besides what he does at shows. Thats like 8 hours a day which is more then most people can say they do in a week myself included these days.