Well, no. There is also the mass of accelerated air which passes just outside the cowl, which will be arrested in the x-direction by the reverser exhaust. That loses momentum also, so that is going to enter the momentum-loss equation too.
No, it's not.
The perception that diverted fan or exhaust gasses cause a "wall of air" which somehow serves to slow the airplane down is largely a myth. Only where such airflow causes aerodynamic losses for the airplane can it possibly serve to slow the airplane, or where some forward component of that gas path exists. It's effect on the free airstream, or even the boundary layer adjacent to the cowl, is largely inconsequential to the process of slowing the airplane on landing.
While re-directed gas path may impinge on the free airstream and divert of slow it, this doesn't cause the airplane to slow. Only the forward component of that exhuast gas path has an effect. It's not a sail, and it's not a solid, attached component to the airplane. It's a fluid, and once vectored by the cascade vanes or buckets, it's done, insofar as any benefit to the airplane.
It would work for airplanes also. Mount the engines in the other direction, blowing onto the wing. Smoothly, of course. And rise into the air vertically. Better idea: move the wing in the air. You'd probably have to make it go round and round to do that though. Wait, hasn't somebody had that idea already?
No. If you're talking about helicopters, find a helicopter that works by mounting turbojet engines on the rotors and using the exhuast gas to flow over the rotor to produce lift. Then again, find an airplane where the same thing happens. Even then, you're talking about something entirely different than considering exhuast gas velocity with respect to reverse; entirely different mechanisms, absolutely apples and oranges.
A rotor passing through the air operates in a very similar manner to a wing passing through the air. This has nothing to do with reverser operation, however.
You seem to have run in circles and are entertaining yourself with nonsensical teasers that do nothing but cloud the issue.
Yes, really.
So now you are saying that "intake drag" is "a component of the ram drag equation", whereas, before, you were saying that ram drag and intake drag were two names for the same thing:
For the purposes of discussion, as explained here ad nauseum, yes.
When considering whether redirected exhaust or fan gasses serve as the chief retarding force, or whether the chief retarding force in reverse operation is airflow through the engine inlet, yes. We will refer to the collective inlet force interchangeably. You're welcome to break it down ad infinitum into numerous components, even to attempt to decide which compressor stage, diffuser, or even fan blade absorbs the most energy from the ram mass airflow influx, but I have no need to do so. Collectively, the drag produced by the various components that compose the total retarding force may be referred to as ram drag, and yes, I also interchangeably use intake drag, for reasons previously cited. Deal with it.