1. It has been his go-to routinely when it has strategic advantage. So with enemies he can take down otherwise? No. But he hasn't shown any hesitancy to use it. He's bitten enemies twice in the past year as a part of the Avengers. Puck doesn't have feats that place his speed as faster than Blade's. Even then, realistically think about how easy it is to bite someone in the course of a fight. Puck would require an immense combat speed advantage for that to be difficult, and feats would suggest that Blade actually has the speed advantage.
We have statements he's resistent to punctures, but as noted, he's also been punctured by a tranquilizer. To your point, it was a tranquilizer that worked on other durable character, but it suggests that he doesn't posses the type of complete invulnerability that colossus and luke cage possess. Moreover the analogy of compressed rubber would allow him to be resistant to some bullets and knives, while not others.
2. The 1929 date is from a max series. Blade has stated on panel that he's over 100 years old and there's been panels of him fighting vampires during world war 2. Their experience is roughly the same.
3. Those are solid fighting feats. I think the main piece, is pucks other attributes seemed to overcome a skill deficit (like against taskmaster where he could use his strength and speed advantage). However he doesn't have an advantage in other attributes in this case. Best case scenario is that they're even in strength and speed, but I do think Blade has more strength and speed feats that make the physical aspect lean towards him. To do a quick run through, Blade has stalemated Wolverine twice, beaten Deadpool twice, and nearly killed an enemy that made short work of Daken. Those are some character I think they crossover with from time to time.
Re: the ironfist punch, I'd put Blade taking a blast that knocked Captain Britain out of the country on the level of Puck taking that Ironfist punch. There's also blade tanking a strike from mjolnir to the chest from Ghost Rider Thor.
3. Re: The bite, my main point is even if we assume that they're completely even in all physical attributes, Blade just has a couple of other super powers that give him an advantage.