I listened to both the original and the slower version. It sounds perfectly normal to the native ear. Even analyzing sounds, every sound you would expect is there. The final t from hundert and the first d from drei are coalesced (so sounding a bit like sechshunder-(td)-reiundsechzig, but this is the correct sound). But it seems you are claiming the er in ...
Since you asked in English, I'll assume you are familiar with English pronunciation. The English words for "stimmlos/stimmhaft" are "unvoiced/voiced". The English voiced "s" is generally written as "z", if you pronounce it you should feel a vibration in your throat.
Pairs of English words with unvoiced/voiced "s" are:
sue - zoo
see - zee
sink - zinc
Falling intonation is the standard intonation pattern in German. There doesn't have to be a special reason to use this pattern for either the sentence end or for marking the end of an important item within the sentence.
In contrary, rising intonation means to alert the listener. If it happens at the end of the sentence, the sentence is a question.
Da kommst ...