My thoughts:(posted 8500 days ago)1. Digital Truth says Tri-X at 200 should develop in D76 1:1 for 9.5 minutes, so perhaps a trifle under-developed, which would inhibit speed a little. Is this developing procedure (developer, dilution, time, temperature) your normal? If not, you are changing more than one variable, which makes it hard to pin down.
2. Is your normal 200 rating for blue photo floods or daylight? If your usual lighting is daylight, this might cause the discrepancy. Many people ignore the spectral sensitivity of b&w films, but it can have a real effect. See: http://www.kodak.com/global/en/professional/support/techPubs/f9/f002_0 360ac.gif
3. My Pentax digital spotmeter (Zone VI modified) consistently gives tests that are about 1/3 stop faster than ISO ratings. I suspect my shutters are just slow. If your meter is, however, consistent (it sounds like it is, since you repeated the tests with similar results) I wouldn't bother to send it out for repair.
4. In any case, if your spotmeter gives you consistent results with negatives that you like using 200, then use 200. Photography is about results, not testing.
5. A film-base-plus-fog density of 0.01 is too low for Tri-X 35mm, so something seems amiss in your density readings. Perhaps FBF has already been subtracted? FBF for Tri-X 35mm runs around 0.18 to 0.25 if I remember right.
By the way, your "-2 stops etc." discussion doesn't seem quite right. Two stops under exposure (and I gather that -2 means closing down 2 stops), means the speed would be rated at 1600. You can figure out if you said what you meant, and my comments are based on the other info you provided.