My reciprocity chart for Tri-X 320 4x5 says that a 1 second exposure should be corrected to 1.5 seconds, a 50% or half-stop difference. If your shutter gives you 0.9 seconds actual exposure at the 1 second setting, you're even more underexposed.
The underexposure aside, your contrast is greater than you would expect. I'd agree you're agitating too much.
Film speed is highly dependent on a number of variables. Meter, metering, exposure, flare, scene contrast, developer, agitation, temperature, color temperature of the light, etc. Starting to test at box speed is reasonable, but don't expect your results to match. My personal exposure for 320 Tri-X is 160. Yours likely will be different, but it will be yours, and once you've pinned down the variables and start to get consistent results, you'll be on your way. Film testing is just that - testing. One test does not indicate a trend. It gives you a starting point from which to compare more data.