For some reason, my blasted computer won't let me see that. It gets stuck.
So can't comment on that, except that I agree that saddle looks absolutely minute on him!!!!
As far as haemotoma goes (spelling dubious!), it will look ghastly for a few days, like elephant man. But for some reason it doesn't cause them much pain - I suppose the swelling protects the injury.
It will go down pretty quick but you will be left with a lump for a while which you will constantly stress about (if you are anything like me!).
Don't even think about retiring him. He is low mileage and has had a few scrapes and issues. So has mine, wither swelling because I went treeless and the pommel pressed down on one side (how stupid was I as I felt tipped forward on that silly saddle, but took no notice!), leg with cut got infected, took three bottles of antibiotic injections to sort it, shoulder had a real issue, cue mucking about good and proper with the farrier ............ the list is endless!!!
Chin up, if he is bucking and kicking, he is not in agony!!