Hi Phil,
You must have a really long runway on your single-engine test, and must be pushing beyond 100% N1/N2.
I tested the single-engine take-off when I first got the model, and did not have enough runway to get to V1, but if I'd had double length runway I think I would have been able to get to VR, but would not have been able to maintain V2.
How are you determining 8500 fpm climb out? The 727 is able to climb very steep angles and very quickly IRL... but maybe not that kind of performance.
The reverse thrust does seem a bit too much, I am able to come to a stop in maybe 100 ft with 3x reversers alone... but I've never flown the real thing except as a passenger, so I'm not sure. I do remember the reverser engaged will throw you forward as a passenger.
The VSI is included in the next SP, per what CS has told me in my tickets. Flying is not impossible without a VSI. Take a Cub up for a spin.
I have successfully flown 10+ hops in my 727-100 with the VSI fault. It's simply this... if it takes 1 minute to climb/descent 1000 ft on the altimeter, you are going at a rate of 1000 fpm. If it takes 30 seconds, then it's 2000 fpm. if it takes 15 seconds, a rate of 4000 fpm. Anything faster than that, and you are exceeding good sense for the aircraft.
As I fly with FSPassengers-X, they will yell at me and I will get bad points if I exceed about 5000 fpm. Thus far, this only happened on one unrecorded flight, when I was verifying the behavior of the VSI.
So yeah, to answer your question about holding a steady 2000 fpm climbout, set your chronograph and count how many seconds it takes to go 1000 ft. If it's 30, then you're doing exactly 2000 fpm.
Perhaps you're right that a failure of VSI would warrant an emergency and immediate alternate landing... but then again, when this happens, pilots must use the method I described above to determine their climb/descent rates when doing so.
A good lot of things are being fixed in the next SP, which would be available fairly soon.
And one should qualify your "legally" statement, as there are many types of aircraft which do not include a VSI at all.
Also, I've not seen the issue you report about the ASI... my ASI agrees within a few knots of what the raw data display shows. True to life, the ASI is not 100% accurate... this is called realism.