You'd be very much ahead to choose a somewhat lower mountain that's on or very close to the equator, rather than choosing the highest mountain many hundreds of kilometers off the equator.
First, the closer you are to the equator the more of your orbital velocity you already have just standing on the ground. At the equator, this comes to about half a kilometer per second (out of a total of around 8 km/s minimum orbital velocity requirement) -- very significant.
Second, most places you'd want to go once in orbit are easier to get to if you're already in a low inclination orbit -- the Earth's axial tilt is already more inclination than you want, but you don't have launch windows of minutes per day (or worse) if you launch into equatorial orbit vs. launching at higher inclination (Florida is bad enough, Kazakhstan is terrible, and Everest is a little further north than Canaveral).
Chimborazo, in Ecuador, is a far better choice. Not only is it actually further from Earth's center than Everest (due to Earth's equatorial bulge), it's practically on the equator, and it doesn't stand among dozens of other similarly high peaks, so it has a much clearer run-up for your maglev launcher.
Beyond that, another answer has indicated why the long, balloon-supported extension to the vacuum tunnel is a bad idea; better to simply have a series of timed doors to minimize air entry into the evacuated tunnel while the vehicle passes, and end the tunnel at whatever point it's no longer practical to support it on the mountain.
Also, don't forget your launched vehicle will still need some amount of rocket propulsion and active guidance, because even if launched at greater than orbital velocity, its orbit will still intersect Earth's surface (never mind significant atmosphere); it will need to have its perigee raised before it completes a single orbit else it will come back down like a Falcon 9 with a second stage ignition failure.
This also solves the problem of impacting air (even at 30 km altitude, never mind the 6 km actual height of Chimborazo) at 8 km/s -- you just don't. It's easy enough to toss your payload above the atmosphere, and only requires a couple kilometers per second instead of the whole 8 km/s. Once near apogee (over the mid-Atlantic, give or take) the "second stage" fires to finish the job of putting the payload into orbit. You've save the cost of a booster -- but watch out, SpaceX didn't have to build hundreds of kilometers or evacuated tunnel and thousands of superconducting magnet rings to do the same...
As noted in comments, you'll need to delete the upward curve near the end of the tunnel; it would produce more G load than the launch itself, and at right angles (one direction is far easier to deal with than two). If you launch at "only" 2 km/s, however, you need a lot less tunnel -- at 3 G, it would be just over a minute of acceleration, and require less than 70 km of tunnel; this could be virtually straight from near Guayaquil to the mountain peak (though that would be one heck of a trestle, even if the entry port was quite deep underground).