Would the alien be strong enough to burst out of Superman's chest?
Not very, I'd suspect. If the entire Justice League ganged up on Superman they could almost definitely take him in a fight. Like, just have Wonder Woman, J'onn, and Aquaman gang up and start pummeling him, and if he busts free have GL drop a building sized construct on him. And The Flash could do all sorts of hit and run tactics, maybe even using Kryptonite in some way. And just keep repeating that process until they've won.
In the premiere issue of Worlds' Finest (of DC's The New 52 reboot), it is revealed not only that the Huntress of the post-Flashpoint universe is Helena Wayne from Earth 2, but that Helena Bertinelli has been long dead and that all the exploits of Helena Bertinelli's Huntress were committed by Helena Wayne acting in her name.

What if they just started writing the Silver Age one like the newer one?
Well if it makes u feel better, that stuff with the jla couldn't have possibly happened in this continuity. In fact, most of her life couldn't have happened. What with the continuity being what it is. So, technically, huntress is just Helena Wayne. Which
means, bertineli never really existed.....at least not as we know it. Better? Worse? I don't know....
What if a facehugger from Alien laid an egg in Superman? How ****ed would the Justice League be against a Super Xenomorph?
I'm sorry, that must have come off as harsh. A side effect of both the current medication I'm on and Geoff Johns being a *****ebag is irritability.
Under a yellow star, the "egg" would starve as it passed thru supermans system.
Agreed.I've always been kind of bugged by how Superman's weakness to magic is portrayed. Like, I think originally the idea behind it was that he's just as vulnerable to magic as everybody else, and that's the take that makes the most sense and seems the least silly to me. But in a lot of cases it's portrayed as him actually getting weaker around magic regardless of what it's supposed to be doing. Like, any enchanted object can hurt him even if what makes it enchanted doesn't involve being used as a weapon.
I'm not sure I understand what you mean. Like, someone enchants some playing cards to smell like strawberries, and suddenly they can give Superman papercuts? That kind of thing?