Your analysis focuses on using HIMARS against RF Battle Tactical Groups. That doesn't appear to be the majority of what they're being used for. BTGs are mobile, so for relatively accurate artillery to be effective per-round, location intelligence needs to be both accurate and recent.

Instead, look at RF logistics. They mostly use rail for moving both armor and artillery ammo. The ammo gets deposited in depots and then is trucked to batteries. There's a trade-off on how far back the depot is from the front line (as in "any potential location opposition artillery might fire from"). The closer it is, the more effective your truck transport (more round trips per day). Further back reduces your throughput - adding trucks and drivers only increases that if they can avoid two-way traffic on a single lane.

HIMARS has been a disruptor of RF logistics, both depots and bridges as well as being used to take advantage of accurate/recent intel - not to mention counter battery fire (the RF does not appear to be using 'shoot and scoot' - someone correct me?). Also, there are come comments here indicating that the HIMARS of 2020 has better capabilities than the one you experienced in the Gulf

I'd agree with Sec. Austin that it's to the US's advantage to deplete the RF's military capability - but it's not just the US's advantage. It's to pretty much any nation standing between the RF and the 'gates' that the USSR pre-collapse was capable of holding with relatively small static forces (logistics haven't been a Russian strong point in, well, ever). So, most ex-Warsaw nations. And the rest of NATO, which has mutual defense treaties with the nations under RF threat.

The real question in any peace agreement is "will the RF keep to it?". Putin would love to be able to freeze the lines now, take more bits and pieces in special ops (little green men) later.

That's a short-term concern. The RF is entering a demographic collapse. In a decade or so, they simply won't have the military-age population to support a major action. I expect Putin is aware of his demographic issue - and it might be why this invasion happened when it did.

I've approximately zero military experience - but I have been trying to keep up.