YAB ridiculous! It's a HUGELY competitive industry where he will be told MUCH more harsh comments at auditions. If he can't cope with that he's not cut out for it. There are thousands if not millions of talented actors who never get more than bit parts/extras work.
It sounds like you have built him up to believe he WILL be successful/famous/'make it' when it would have been far more sensible to encourage BUT in a realistic way. So that he was prepared.
A friend of mines' daughter is STARTING to find success in acting. By which I mean leading roles in smaller productions, supporting roles in larger productions in New York, roles on commercials, small but speaking roles in well known tv shows in USA. She's mid twenties and has been performing since her early teens, been to drama school and sensibly trained in a behind the scenes craft which allowed her to stay in the industry (and make connections) even if she weren't getting acting jobs.
She's had auditions where she hasn't even had a chance to utter a word and...
"Nope next!"
"Stands wrong next!"
"Too short next!"
Then there's all the criticism of how she's portrayed the parts - but not every actor is suitable for every part.
But only her and 2 others from her cohort in drama school have had ANY real noticeable success. The rest are working behind the scenes, doing extras work or (and this is seen as doing quite well) are 'jobbing' actors getting regular but not big parts on well known tv shows and in theatre.
Go look on IMDb, even very famous actors have a long list of much smaller parts before AND AFTER becoming famous, because they know that's the reality. And they sensibly know 'bills need paid' that's real life.
Can I ask why he hasn't seemingly done much toward "his dream" before now? Most wanting to act have been involved in extra curricular drama classes, dance and voice coaching, lots of auditions for other parts (and would know if they were any good) way before 18. - I wrote that before reading about his auditions etc. Did the fact that he rarely was chosen not show him or you he was unlikely to succeed in this area? Did he work on any feedback he was given indicating the areas he wasn't up to scratch in?
There's a difference between not standing in the way of his dream and giving him false hope.
If they're asking him to reconsider rather than kicking him off, that makes me think more lack of effort than lack of ability. Which comes back to what EXACTLY was he told? Was he recommended to do something that would help this aspect and he hasn't done it?
"He also finds certain things really cringey" that's WHY they do these exercises to remove their being overly self conscious. Let's face it many acting jobs are faintly ridiculous (action movies, medical dramas, fantasy genres, hell Shakespeare where you might end up playing a tree or a fawn!) they need to be able to set that self consciousness aside to do the job. It's also so they connect mind and body properly, a real awareness of how their body moves. Plus so they can manage movement directions AND remembering lines.
"quite dry and analytical so he has questioned some aspects of the course." Questioned or criticised in a way as if he knows better? The latter REALLY doesn't go down well from 1st years on any course.
Lee Evans actually works very hard on the physical aspect of his performances so while it may LOOK clumsy, ungainly it is STUDIOUSLY so.
I think your idea of taking a year out is good BUT I think only going on a load of auditions will NOT address the issue.
Being able to use your body to express the character of the part you're playing is essential. He needs to be able to make his body do what he needs it to. He also needs to be able to move about a small stage in such a way as he's not disturbing props or putting other actors out of sync. If he can't even hit a mark consistently or move between marks he can't do the job.
As for "loads of actors didn't go to drama school" just not true. Most successful actors have at the very least performed in highly regarded amateur performances/clubs (eg footlights) but a huge number, even those from acting families have been to Rada, lamda, Italia conti, Yale school of drama Juilliard etc.
"Similarly, being under 5'6" didn't stop Wayne Sleep succeeding as a dancer..." Sorry that's nonsense dancers ARE small he'd have had less success if taller.
All the famous tall actors people are mentioning actually DO know very well how to control their bodies. Where they have done 'funny' or unusual movements that HAS been part of the character they were portraying and actually likely took a lot of experiment and rehearsal! Missing the point op's sons Tutors are making completely.
Plus in some cases they've been LUCKY to find a niche that coincided with a zeitgeist moment. Eg can you imagine John Cleese ever playing a serious romantic lead? Or Stephen merchant for that matter? Or playing a genuine detective role like morse? There's an awful lot of luck involved. Such that there are even actors who are very successful in one particular role and then never again after, kind of like acting one hit wonders. Like Jason Biggs, Mark Hamill, Ralph Macchio
"Big fish, small pond sort of situation." Exactly.
"The OP telling her son that it’s actually the tutors’ fault anyway because they didn’t teach him right is not going to help him to take responsibility for his own learning and development." Definitely agree with this.
"that is down to his physicality not the teaching" not necessarily if he's not been working sufficiently on this aspect. There are lots of tall, long limbed actors several have been mentioned here BUT they learned to control their movement and even use that to their advantage. There's a danger if you're saying things like this to your son that he'll think nothing can change so there's no point him making an effort with that skill.
"You are placing too much emphasis on how the tutors are awful and how even him failing assessments isn't his fault it's just because he's tall." Absolutely agree with this. Don't encourage him to deny or deflect it won't help him.
In addition to pps saying he's probably misreporting what exactly was said (either deliberately or clouded by emotion) I'm also sceptical that this is the first time he's been told he's struggling in a particular area. Uni's don't want failures at any stage so I think it's likely he was told, probably on several occasions, to work on X and hasn't done it and then failed the connected modules. That's on him.
(That story about Harrison ford is a myth btw he'd started acting at uni and had been acting and auditioning for a good decade before Star Wars.)