Strange "hey siri" and outgoing SMS audio message issues!

I've been having an issue for *months* - and today decided to try to fix it. I've been googling, testing, etc. for hours... no results. This is going to be long-winded/detailed, not sorry. I rarely need to ask for help with tech issues. I'm the one people usually come to when they have tech issues given my work and personal experience. This one though - this has me baffled.

This is an iPhone X, one of the earliest ones manufactured, I preordered it the minute it was available and have been using it ever since.

At the onset, the issue seems as follows: "hey siri" doesn't work, and my outgoing SMS audio messages are so full of static that they're unintelligible to the recipient.

I noticed that "hey siri" stopped working a long time ago. I didn't use it frequently, one day I noticed that it just didn't work anymore. I don't even know how long ago it stopped working. My lifestyle and line of work at the time didn't put me in a position to need it much, so I shrugged it off.

Due to lifestyle and work changes, two things happened within the last few months:

1. I made a friend who likes to keep in touch primarily by exchanging SMS audio messages. I quickly discovered that if I send her a SMS audio message over bluetooth (from my car's head unit or my earbuds) she can hear my message perfectly. However, if I try to send her a SMS audio message with just the iPhone's microphone, the message is so full of static that it is unintelligible.

2. I need "hey siri" to work again. It would literally make my current line of work safer to be able to have it working - but I can't even get it set up! I tried the usual tip: settings->siri&search-> toggle off and then on to set it up. When I try to set it up though, it always says "Siri didn't quite get that. Try again."

Naturally, most people would come to the conclusion that there's something wrong with my iPhone's microphone. I can not stress this enough: this is not an issue with the iPhone's microphone! How am I so sure? Well, because I can record a voice memo with the iPhone's speaker with perfect clarity. I can also record a video with sound and the sound is perfectly clear. Voice-to-text "works" just fine as well (as well as it ever does, I suppose - lol! But it does "type" words that are a reasonable approximation of what I say when I use voice-to-text.) I can also talk on the phone and the other party has no trouble understanding me. (I always have trouble understanding them, but I imagine that's more of an issue with my cellular plan - totally separate issue.)

At first it didn't occur to me that the two issues might be related, but now that I've been trying to fix both, it occurs to be that there may be some way the software is handling the speaker in the case of "hey siri" and SMS audio messages that may be similar. I can't conceive of any reason why this would be the case, but I also can't think of any other cause for this particular set of issues.

... and google-fu as I might, I have been unable to fix this problem.

Unfortunately this particular phone is overdue for a replacement. The battery is absolutely shot (I live in one of the hottest places in my country and given my current line of work I can't exactly practice proper battery hygiene), and a few days ago I actually managed to crack the front glass on the device (I managed to come down with a medical condition, the medication my doctor gave me weird muscle twitches and my arm literally spasmed and sent my beloved X onto the concrete). Stop right there, before you say it! Remember, I've been having both of these issues for a 2+ months now. The screen crack is completely unrelated, and fortunately appears to have absolutely no impact on the function of the device itself.

Thank you for any assistance!