Ok. How about the other 2 question?
I'm not a super duper expert but I've got about 700 games with him.
Joker has 2 speeds all in or keep away.
Gunshots are surprisingly fast, like, if you don't play Joker go play him and you'll see how much it trades favorably with.
Here's just one example, it can punish in between two Harley gunshots if timed properly, it can punish FTD, it can punish Omega beams, it's just not a bad tool.
IF you can get them to respect gun shots, then you can mix some canisters in there, especially if you're opponent doesn't have a fast way to punish. You can also throw it meaty in some knockdown situations.
So his zoning is a smidgeon better than ok. It's good, just not better than Fate, Deadshot, Arrow and Starfire. Other characters it's dependent on the range and how good your reads are.
Point is, it's super useful.
Joker has very poor neutral Game. He's got T-Rex range and no really good advancing moves. Things like f212 are so telegraphed that it's easy to react to since it doesn't really move forward at once.
If you like footsies don't play this character. You can win up close or far away at times but playing mid range is suicide.
That being said, you do have some options. Obviously Crowbar can be meter burned for armor and sometimes you might catch someone off guard but you can't rely on it.
Teeth can be punished at times but you can drop them in neutral against some characters to limit advances I'm thinking for like Bane and Grodd.
Joker's D2 is slow but the range ain't bad and you can special cancel it in a small window. So you can read block and be safe with Crowbar (against most).
Finally, his up close game is riddled with gaps. You might think you can 32 into special but you can't, you will get d2'ed by anyone that knows that match up. So lots of 21, it's a mid string that's plus and you can cancel into neutral or special depending on whether you hit. There's also a gap there.
Because of his gaps you're gonna have to mb some f3's in there to get people to respect it.
You've got a pretty good sweep, it's not Scarecrow's but it's got solid range. Some players are gonna try and back dash everything you do, don't let them, gotta keep em honest. You can catch some with your jump ins. J3 has got great range and you can throw some teeth after it and put them on the defensive. J2 is a cross up one but it's got a junky hit box, if you don't have trait activated you're liable to whiff a lot instead you can use j1 which has a pretty good downward sloped hit box.
In the corner there are a bunch of different things you can do I've seen very few Joker players play the corner the same but the gist of it is knock em down and keep em down. Reset, teeth, reset, teeth, armored f3, teeth into cross up, it depends on what character you're playing against. For some the corner can be a death sentence for others not so much. My advice is to go into practice and see for yourself what works against what wake ups.
But you can't keep the corner every game. There are no legitimate mid screen set ups. One way or another they are all avoidable but that doesn't mean they aren't useful. If you can condition your opponent to do the same escape each time you can use it to your advantage either by bettering position or punishing. 2 examples: one Red Hood player decided he was going to back dash every knock down/teeth set up mid screen. You can catch that with a jump in or a well-timed shot or in some places a crow bar. If they decide to delayed wake up you can start delaying teeth and going for ambiguous cross ups with teeth, if they want to wake up you can bait and punish or just stuff it with mb3 or f3. Point is, they make a decision and you make a read. Remember you can always do teeth into nothing, don't even move. Just watch what they decide to do and plan for it.
Your wake ups fucking suck. There's no two ways about it. Don't ever do crow bar because you will get stuffed. Parry gets beat by jump ins and lows and it can be stuffed. It's garbage and it's not even invincible and it doesn't work on cross up f3 moves which is super duper lame. Your options are block or make a serious hard read, I mean, like Cheetah players use f3 like it's going out of style because it's so good for her but a character with a low starter an overhead and a nasty jump in like Flash will maul you on wake up. So guess right. His greatest strength is also his greatest weakness.
This wasn't a super tech heavy outline but that's basically what you're doing.
P.S. Play like a goddamn lunatic, get into the character, make yourself unpredictable.