But I am wondering, is it normal to clear ones throat a bit loudly, say "excuse me, there is a queue!" or how to you normally handle such situations?
Да, можно сказать: "Сейчас МОЯ Очередь" It's better not to wait while they jump you in.
You can also adress a relatively young man "Молодой человек" - it will be rather mild.
"МУЖЧИНА!!! move away from there!! Right away!!! " or something like that.
Yes, it sounds rude, but we cannot change anything.