1) Does the Klingon language have prefixes for these subject/object combinations?
you(plural)/none etc.
The answer is yes.
There are bound to be tables of all the pre- and suffixes to be found on the internet.
here's one.
2) Question about adverbs
How are you going to say?
He speaks very much// loudly// proudly// poorly// forcefully// clearly etc.
refer to the same page, and look at the suffixes...
3) Do they have interpunction signs like comma and/or full stop?
There are some, which again (Klingonska Akademien is a wonderful site) you can find on above page. Normally though, Klingonists use the Romanised version, including normal commas etc.
4) How should the klingon "S" sound like??
Like "s" in sun/soup or like the "s" in she/Sean??? As much as I understood it should sounds more like "sh" sound, but in the films and series Qo'noS is pronounced with simple more or less s like in soup/son.
Although the series and films are considered canon, they are also appalingly bad at (pronouncing) Klingon... The proper way to say the
S is using the S of Sean, or indeed the Sh of ship and shoe.