Re: Slipping to the inside
It has to be second nature. If you have to think about what to do, you're going to get hit. That short left counter that I mentioned needs to be practiced on the pads with your trainer. Your opponent is only human, and when that left lands, he's going to freeze up for a second.
Get the movement down, use just enough motion to slip the jab and to get in closer. When you're inside, don't pause, step in and snap that left quickly with your body behind it. Punch through your opponent, don't just flick it out there. When your opponent is jolted backward for that brief moment, you should have some openings to take advantage of, just keep your punches nice and short and hit him where it counts.
Now if it the left doesn't land right, you might want to fall into his left (your right) and tie him up.
If you hear a voice within you saying that I am not a painter, then by all means paint and that voice will be silenced.