High Altitude simulator accuracy in X-Plane

In X-plane 7.0, I have reached 240,000 ft in altitude with an F-16, and
290,000 with an SR-71. Now after 80,000 where the atmosphere is thin,
apparently the jet engines with afterburner are still pushing the
aircraft with the same force (no oxygen around).

I wonder if this accurately shows the possibility with an F-16. How
high has anyone gone with one of these fighters?

Secondly, as you dive into the ground, then level off with the
afterburner burning, somewhere at 800knots, aircraft start accelerating
again as if theyre functioning as a ramjet or something. Its hard to
push an F-14/15/16/18 to beyond mach 1 at level flight at sea level,
but once you push it beyond that by diving and leveling off, it really
accelerates at level flight to 1900 knots or beyond with a strange
whooshing sound. Most airrcaft are hard to control, especially the F-22
and the F-14 at these speeds.

Is this real? Can you really push an F-16 at sea level on level flight
to beyond mach 3 in this manner?