What turbo trainer model have you got?
Does it support the ERG training sessions, where you stick in a single gear (typically small ring and mid cassette) and then Zwift changes the power resistance?
What "trainer difficulty" (slope feel) are you using in other modes besides ERG? Default is 50%.
There's regular TT races throughout the week on Zwift,
https://zwiftpower.com/events.php gives you the schedule, sign up and connect it to Zwift and Strava if you fancy competing for ranking points.
"Flying Cheetah" do weekly longer TTs that would suit your 44Km target, for example, this week it's
https://zwiftpower.com/events.php?zid=272556