Had a similar issue with my 2004 TJ. The P1698 basically means there's no communication between the TCM (Tranny Control Module) and your Engine Control Module (ECM) which an initial diagnoses would point to faulty TCM or loss of power to the TCM Bus (Plugin on the module). Since there is similarity between this code and the other 2 codes you are getting which is a loss of power from the SKIM buss (which I believe stands for Smart Key Immobilizer) for your ignition key and the other is loss of power to your cluster buss for your dash, I believe you there isn't a problem with your steering control mod, but rather a problem in the wiring for your head unit you installed. I would double check the wiring. You say you played around with the ground and it went away? Which ground wire is this? Head Unit Ground?
This is what I would do in order of how I'd do it:
1) If this is the head unit ground I would first check and make sure it is in fact a ground (I'm not doubting your knowledge of it). You can do this by getting a multimeter or test light and checking from the wire to ground and see if you have any voltage and be sure you have your key switch in the ON position when checking this, bad thing about this is that if the wire is how and you don't get voltage then it doesn't mean it didn't at one time and it may have already shorted killing power to it, check all your fuses and insure they are good.
*If you do have voltage then this is your problem, this would be a direct short causing all your problems and could possibly be your switched wire, or your memory wire for your head unit which are the only two wires that should have power going to your head unit with the exception of the possibility you have a factory amp which is possible and in this case you have 3. Typically if I recall the "memory wire is red" and the "switched wire is yellow" (possibly vice versa) on Chrysler vehicles and ground is black, unless the GC's are different from the dakota, xjs, and tjs I've had where all were the same.
2) If it doesn't have power and you checked the fuses and is in fact a ground wire then I would put a multimeter on it and Ohm the wire to a clean ground and insure that it is reading 0 ohms or gives you a continuity buzz on the meter.
*If it doesn't read 0 ohms (or very little like 0.2 ohms) then you have a broken ground which could also be a problem which would explain all the codes you have. This won't necessarily mean this wire is physically broken (which it can be) itself because it may tie into a bundle of grounds that ground all the other components like your Cluster, TCM, and Skim to the chassis. So in other words you have a chassis ground broke or loose one on your frame/body which can be anywhere on your vehicle, including the firewall. So you would have to check all those.
3) If the above two check out then your going to have to dig deeper. Before you dig deeper I would first check every single fuse in the interior fuse panel and the engine bay fuse panel to ensure that none of the fuses for the TCM, Cluster or Skim are blown which will also account for your loss of communication between all your buses. This all may sound confusing but all your looking for is that all your modules have power and are grounded in the simplest of terms. So check all your fuses.
If you have to go deeper than this by checking buss voltage and such, just let me know and I can tell you more on how to track this down.
For you to have gotten all these codes at once leads me to believe that it is for sure a ground or a fuse. If it is a fuse then it blew for a reason, but whatever the reason, replace it and if it blows immediately then the ground wire is a hot wire or another hot wire is shorted if it doesn't then problem solved, don't lose sleep. lol.
Post back as you go.