First, note that "be" here is used as the main verb "to exist": discoveries and insights that would not have existed without the collaboration, etc. This should simplify your grammatical analysis.
As for the subjunctive, "would not have been" is the consequent of this conditional, and it would normally be the antecedent that would show a subjunctive mood. But the antecedent here is a noun phrase ("the collaboration").
If we change it to a verb (and also modify the sentence to allow a verb that shows subjunctive inflection), we'll see that in this irrealis context, a subjunctive is perfectly possible:
This discovery would not be possible if I weren't collaborating with machines.
(Note that many native speakers are losing the subjunctive in casual use and would say "wasn't" there — not because it's the wrong context, but because they don't use the subjunctive at all. In Canada, my work often involves hearing prayers, and people often say things like: "I pray that this is a good day." Should be "be".)
Your question about the tense is good. Yes, "would not be/exist" would accord better with the tense of "this can lead to". The writer does a mental shift from the beginning of the sentence in the abstract/present to a time in the future already looking back at something that has been created. And that is not ideal style, even if it's not egregious.
"Otherwise" works pretty well. I would place it either before "be" or after "impossible", probably preferring the latter.
that would be impossible otherwise.
However, there is a slight logical leap here. "Otherwise" means "if something were not the case". In your sentence, if you remove "the collaboration", you have to scan back through the paragraph to find what alternative is being negated by "otherwise". If you do so, you'll find that the most logical candidate is to negate the existence of intelligent machines, but their existence isn't explicitly predicated. What is predicated is that their convenience and efficiency can free up human time and energy. Thus, unless the read processes it thoroughly enough to realize this, "otherwise" strongly suggests that the discoveries and insights would not have been possible if convenience and efficiency didn't free up human time and energy — and that hypothetical seems hardly worth speculating about, being close to a contradiction in terms.
Hence, if you were to use "otherwise", I would try to keep some reference to is actually being contrasted: the collaboration or the machines' existence (or, if I read into the paragraph more than it really says, our hearty acceptance of intelligent machines, or what have you).