C'est tout ce que je veux dire dans ma présentation.
This is grammatically correct but not idiomatic and not really semantically correct. Since you would be saying this at the end of the presentation, when you've said everything you had to say, vouloir dire should be a past tense. And vouloir dire is not really the right thing here, for a more subtle reason: it would relate to the semantic content of the presentation (I've presented the ideas I wanted to convey), but here you're referring to the actual words rather than to their meaning, so the vouloir dire as an idiom doesn't fit. Vouloir + dire would fit, but because the two are juxtaposed, people will hear the two-word idiom and not two separate words. Instead, we would say
C'est tout ce que j'avais à dire dans ma présentation.
Purists may require « mon exposé » instead of « ma présentation » for a presentation. The noun présentation only really works when the context mentions what is being presented, but that may no longer be true these days. If this is a French class I'd stick to exposé, but at my workplace (where franglais is unremarkable) people would do une présentation and nobody would blink an eye.
This is correct and idiomatic. In a presentation, if you want to invite people to ask questions at some point, saying « Questions ? » (with a raised tone, as always in French when asking a question) and pausing for a few seconds is the normal way.
However, at the end of a presentation, you should say this in a more formal way.
Avez-vous des questions ?
Unlike other respondents, I would not use « Des questions ? ». It isn't a big deal but it would sound a bit strange.
If you want to invite comments, « Questions ? Commentaires ? » doesn't really work. It's technically correct, but it's too curt.
Avez-vous des questions ou des commentaires ?