Correct math used on top of bad assumptions is only helpful if people actually hold those bad assumptions.

Evolutionary biologists don't.

I could equally well argue that a modern airliner was created by God, not humans, because no human or even groups of humans can create a device as complex as an airliner in one go.

That's true! But people don't create airliners in one go. It's both a process of gradual refinement, and assembly of pieces that were not created de novo but refined and optimized before being added to the airliner.

So Lennox's calculations are, at least as you've conveyed, approximately irrelevant to the point, except as a disingenuous argumentation tactic.

Regarding Jesus' resurrection being essential, no, it isn't essential except to Biblical literalists whose views are already disproved by zillions of other things. Any view that admits some degree of human corruption of divine revelation, or a large degree of allegory, can handle a non-resurrected Jesus. It would be a pretty large doctrinal change, but arguably less than the Catholic/Protestant split where the two sides can't even agree on the nature of divine revelation of God's word.