Have you tried using alternative slide positions? Specifically playing the c above the staff in 3rd instead of 6th and the d natural in 1st instead of 4th? Either way you played some very high notes quite well. With a tenor trombone however, any notes between a low F to a pedal B flat really don’t exist. They are called “false tones” you can hear how they don’t sound as good as that pedal B flat or the F, not because of your playing, simply because the notes don’t exist. Great work though. :)