Hey man. Read your blog.
I'm kinda in the same boat - 30s, never played on console, don't even know which end of a pad to hold. The difference I guess was that I was into shooters competitively (Quake) but that's a very different genre. I suck at shooters now too.
First, keep repping the Yellow Bastard. Sinestro Corps! I main him too.
Don't sweat the hate. People hate zoners in fighting games. Most think zoning is boring, and few understand what it takes to do well in the neutral game. You're doing to get a lot of smack talk, a lot of disconnects, and generally bad attitudes all around. It's all irrelevant - what you're looking for are the people that will give you the GG or a bit of technical advice - if you get talking, ask them for a set, and maybe you'll build a network of people to play against so you won't have to be exposed as much to random hate. Generally, the better players get, the less of that nonsense they're likely to hurl at you.
Second, try a stick. For us old klutzes it may help actually. A stick is VERY hard to learn coming from a pad, but if you're someone that has never really learned to play on a pad, it may work better. Sticks are slower than pads, but offer more accuracy. For a game like Injustice that's not overly technical pads work just fine, but if you want extra accuracy stick is the way to go.
Third, use training mode. Seriously. Nobody is born being able to do combos. You hammer it out in training mode hours at a time. I'm just getting into this game as well, and I set aside time each day in training mode to get combos right.
You want to practice wisely - pick a relatively simple, important bnb, and get it down one step at a time. Don't try to do the whole thing at once, and when you fail, you want to look at your input display and see what you're doing wrong. Also remember that you will fall into habits right away, and if you do a combo wrong and mess it up, chances are that's what you'll be committing to muscle memory. You want to stop that right away before if becomes a bad habit, otherwise you'll screw up that combo in that way EVERY time. Look at the input display and diagnose what you're doing wrong, then fix it, for each input in the combo.
I suggest simple, practical bnbs for your most common combo starters: b13, b3, d2, f3, d1, 111, 22, and air axe. A combo like b13 j2 22db1 b3 j2 b213 is a good place to start, or b13 b13db1 b3 j2 b213 or even b3 j3 b213. Start simple. Don't try the b13 b3 combos that are posted here, that link is very tight.
Lastly, remember that the neutral game is just as important. People fixate on the combos because they're flashy, but it's spacing, blocking, and general fundamentals that win matches. Footsies, in other words.
Now this is a big and complex thing to lay on someone totally new, but if you want real fighting game fundamentals, this is a good document:
http://sonichurricane.com/?page_id=1702
It's mostly about SF, but it applies to fighting games in general. I use a lot of this in Soul Calibur and that's about as far removed from SF as anything can be. Even there, the concept of baiting whiffs and punishing them is universal and central to the game. It's a bit of an advanced topic though. Very advanced, actually.
Don't give up - fighting games are really complex. As in, nobody makes games this complex anymore. People want instant satisfaction, which is why you get simplified kiddie games like modern military shooters, where anybody can every once in a while get some points in. Fighting games aren't like that. You'll have to do your homework, and that learning curve initially is more like a learning cliff. But for some of us, that only makes it more appealing, and when you do start to understand this stuff and pull it off on a regular basis, you really feel like you've learned something.
I think this game will be very big - it has a ridiculously powerful IP behind it that appeals greatly to non-fighting-game fans, and yet unlike Marvel it is a more straightforward game that's easier to follow. This makes it a far more spectator-friendly game, and given how streaming has taken off, that's very important. Gamers are becoming entertainers, and this game can be a very powerful platform for a lot of gamers from many different backgrounds to reach out to people. And as a new player, this could be a very good game to learn on.