noting that all my stabs are simplistic...

I think when the 1 MarDiv was tracing down the remnants of the fleeing North Korean Army north of Wonsan in 1950, we were engaged in IW. We were again in early '51 when we and the 5th RCT [1] hunted down the remnants of the same Army left behind in far south near Pusan due to the US / ROK push northward in the fall of '50. They had reverted to using guerrilla TTP [2] and were not attempting to move north [3].

When I went to Laos in 1960, I was engaged in a Stability Operation (which entailed a very minimal amount of IW). In Viet Nam in early '66, prior to the bulk of the buildup, same situation. Later in that year, it morphed for several reasons into more IW and less SO. When I returned in 1968, we had CW (generally less Tanks), pure and simple and little concern in units for SO. That, after Tet, pulled down rapidly to IW as opposed to CW -- and SO was ramped up [4].

To me, the 'classic' definitions are appropriate, simple and not ambiguous. CW is major military force using current technology in moderately to highly intensive combat. IW is characterized by one or both opposing sides using what are conventionally called guerrilla TTP. Stability Operations are as you described and may also involve a spectrum of force through none to simple Police or constabulary effort through Paramilitary Constabulary effort to IW in varying intensity and, rarely, up to CW. That said, it must be acknowledged that variances in that are, IMO, of small concern. Most words in the English dictionaries have multiple definitions and that seems to be acceptable [5].

NOTES:

[1] The 5th RCT in 1950-51 contained then CPT Hank Emerson, who from that experience probably developed his Checkerboard Theory of COIN Warfare. IIRC, he refined that theory and published it while at Leavenworth in 1963-64. It should be in the Archives there.

[2] I use the phrase 'guerrilla TTP' as shorthand for any combat effort by a force (organized, uniformed or not) that uses stealth, evasion, clandestine operations and short sharp actions while avoiding decisive commitment against superior force as a combat norm. Their actions may include infrastructure destruction (human and machine), attacks solely on opposing military forces, attacks on any opponents to include civilians, terror, intimidation and other tactics short of fully engaging major forces in combat.

[3] Sort of an aside to your question but somewhat appropos, I think. With 1 MarDiv and with the US Army in Korea, note the changes in a short period from full bore conventional warfare involving defense against Armored attack to a major offensive operation entailing full bore urban warfare to IW to CW against a different enemy with very different TTP to IW and back to CW. This is why I contend that the Armed Forces of the US are completely capable of conducting full spectrum warfare. If a marginally trained crowd could do it reasonably well in 1950, with todays training we should be able to do it very well at a high performance level.

[4] Again, note the sliding between categories of combat. US units translated between the various forms of combat and other operations relatively painlessly and generally fairly effectively. Most failures I observed were not at the unit level but were command failures at Division and above. Something to ponder is that most Bdes did well; most Divisions did not.

[5] Reasonable people could disagree with me on some of that transitioning between forms of warfare -- and warfare itself is constant evolution. For those two reasons, I think that a quest for excessive accuracy in terminology is probably not possible. That does not mean we should not try to be more precise, simply that accord may be difficult.