We use perfect tenses before temporal 'since', not simple or continuous ones. The aspect of the word 'since' matches perfectly to the perfect aspect. This is perhaps simpler than you might think.
Those are both wrong.
The fact there's a time adverbial is irrelevant. Think of this as an example of the following pattern:
it + is/was + time phrase + since phrase
This is the pattern mentioned on the dictionary page you linked to. In terms of meaning and use, the simple aspect in this pattern is identical to its present perfect equivalent:
It's ten years since I rode bike.
It's been ten years since I rode a bike.
These two sentences are synonymous. You may think of this pattern as an exception that must be explained, or just accept it as a kind of non-standard expression.
I disagree with all of this. First, the sentence is ungrammatical in my book. Second, I can't see how the 'since'-phrase there is causative (Do you mean ... since he had an accident?) Third, how can it be both temporal and causative?
This sentence is no good.
I think only the first is properly defensible.