In German, there's semantically no differences between preterit and present perfect.
That said, in German it's way more natural to use perfect and there are certain use cases where you'll go with preterit. Modal verbs, for instance.
In your example, it's pretty fine to interchange preterit and present perfect.
It's difficult to explain when preterit is fine. There's a question here on GLU asking for when to use imperfect and you'll notice that wissen is one of the verbs on that list.
To make things worse: that does not mean that all instances of wissen would be said in preterit.
In respect to the dass-clause. There's a significant difference between using kann and konnte. The former is present tense, the latter is past tense. So, while in the former one you still can go, the latter one indicates that you cannot go any more, because it's too late.