All of this stuff should be in your handbook,a nd it's your responsibility to read the handbook, not the University's responsibility to spoon-feed it to you. Sub-50% is not acceptable, missing exams because of work is not acceptable (I findt his absolutely flabbergasting).
The other thing here is that you have to take what an individual lecturer says with a pinch of salt. Odds on they don't know a) the extent of this issue and b ) the procedure to deal with it. I see this every day. I know our place's procedures inside out because I am the academic contact who deals with them. The rest of my colleagues do not, and wouldn't have a clue where to start. The process is broadly administrative and barely involves academics at all outside of the programme directors and specialist academic leads or advisors. They just see data, and unless presented with sufficient mitigation to the contrary, will make decision based on this data alone.
It is a little strange that the process has jumped stages so quickly, but it's not unheard of and it could well be because the administrators see the consistent non-engagement (from their POV) with the process and the course as the key issue. Missing the exam will have really hurt any point you think you had, it's bonkers that you'd do that, and in my institution, missing an exam for work would pretty much guarantee an escalation.
As above, you need to go in and speak to them honestly and frankly about this, and even then I am far from convinced any appeal will succeed. At the end of the day, if you can't make the time to sufficiently engage with the course, you probably shouldn't be there. I'm not saying that to be mean.