Multiple problems, I hope related

Just did searching, found some thing here and there but it is still difficult to make out what people are saying sometimes because I guess punctuation isn’t in these days. Also my problems are multiple and I don’t think it is the tranny or the engine. Should be something minor-ish.

Background: I had to pop out the gauge cluster before and when putting it back in I had trouble hooking up the speedo cable back in. When not hooked up to the speedo, the car throws the S3 blinker after so many feet, I know that much.

I was just picking up a Tsudo exhaust from a member on these boards and on my way back the car started acting up. This is the first time I took the car for a 2 hour highway driveway (there and back, combined) on such a cold night. Multiple things happened, and I am praying these are related and not costly to fix:

CEL went on
Speedo dropper to 0
S3 light started blinking non-stop
Cruise control disengaged

I stopped the car checked oil, seemed low. Started, everything but speedo fine again, started going slowly. S3 blinker came on (as expected), and after a few the CEL came back on.

Took the first exit, dropped a quart of 10W-30 in there (from memory, I guess I actually needed 5W-30 but it’s not a huge difference. Correct me if I am wrong). This took care of CEL.

On my way home I still had the S3 blinking, still had speedo not working at all. But another thing happened, at 60MPH the temperature gauge would go down to almost the minimum, i’d say the needle at one point was 1/8 of an inch away from MIN. At city driving speeds, the temperature climbed to the usual - just below the middle. (I swear it is as if the damn thing is reversed)

Could highway vibrations have rattle the speedo cable off the cluster? Especially if I didn’t ‘click’ it back on properly? Also, does it sound like a thermostat problem? And finally, I know nothing about cars (almost, so bear with me) but the CEL light is a reasonable response to the engine being low on oil, right?

I will be checking the codes as soon as I can tomorrow. I am pretty sure that both my engine and my transmission are sound, the car performed flawlessly as soon as I added oil. And I am one of those paranoid freaks that know every rattle by heart.

Thanks guys.

EDIT1: Ripped the interior out, pulled the cluster and whaddayaknow - the speedometer cable is broken. I did pull on the cluster to get it out and it did break when I was doing it, but it was hella fucking weak and mad kinked or something. I don’t know. About to get a quote from Acura on how much it costs to get a new one and I know for a fact I saw a teg tip on this. To be updated.