"8 days worth of missiles" is an estimation of course, and even if it's true, it's only true until we make more missiles; which is no doubt happening. The money is flowing, so the missiles are flowing.
Macgregor is pragmatic; not "pro-Russia". Even Gen. Milley (who was fully behind support for Ukraine) has said that there isn't a military solution for them. That made a lot of people angry at him; but at some point you have to face reality that it's not in anyone's interests keep this thing going indefinitely. An immediate cutoff of support allows Russia a more rapid path to conquest and leaves the US and the west in an undesirable situation; so that's probably not going to happen at least in the immediate future (as he said with his "hot air balloon analogy).
I do think he underestimates Trump, though. I'm not jumping on the "YAY EVERYTHING IS FIXED NOW THAT TRUMP IS PRESIDENT" bandwagon; because that's a bunch of garbage; but if there is a way for a good deal that finally dumps this war he will find it.