I don't know if your loader will work in Classic99 - it might - but Classic99 has a hack in it with respect to the remote jack handling in order to start WAVE files at the right time -- your wave file won't play unless Classic99 sees a transition from OFF to ON on the cassette remote jack. The debug should reflect this.
I tried a few times, but did not work in Classic99 either (only the normal Basic loader works, but then nothing happens when loading the 1200 baud file, I tried already with a prepared 1200 baud tape).
I have not tried the other emulators (V9T9 and PC99, etc.) to see if it works for those emulators.
It seems that JS99er.net is saving the 1200baud files correctly (that would help people who want to run these on a real TI, who only
have a TI+32k + cassette player).
but then how do you get it to a cassette player or is it as simple playing the file and save it? (normally there was a sensitivity level for it?)
(I still need to try a Smartphone and to see if it loads into the TI, but
Not sure how many people around would use this TI+32K+cassette option, but it is quite fun (I found the Funnelweb loader also fun todo).
PS. Sitting at an airport right now, and love the new JS99er.net version, well done, nice layout.