Articles

It does not sound very idiomatic and actually sounds like translated French if you leave out the articles. Though it does not seem so, you could say the articles in English have not been left out either, but since the zero article is used, you cannot tell the difference. However, let’s say you asked if there were ‘any questions’. In that case you would not leave it out in English either:

Any questions?

Now, in French, I suggest you keep the articles intact.

Des questions ? Des commentaires/remarques ?

(Note that in French you use a space before the question mark, as well as the exclamation mark and semicolon.)

However, the phrasing above is fairly direct and not exactly idiomatic. English is a often uses more direct utterances than French, and often uses fewer words to express similar ideas. So, if you are actually giving a presentation, I would not elide the first part of the question either. Even when translating a text containing this phrase, I would, if the space allows it (which might be tricky in the case of subtitles, for example), translate it like so:

• Y a-t-il des questions ou des remarques ?
• Avez-vous des questions, des remarques ?

Ce

The ce is needed indeed, since que does not have a direct antecedent. If you were to add the antecedent, you would not need ce:

… les choses que je veux dire …

Dans

Yes, the word dans is perfectly fine here. Another common phrase to use is à propos de, but it would be followed by the subject of your presentation and not the word présentation itself.

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.

Questions?

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 ?