A lot depends on the flock from which the egg came from. If it was of mixed breeds, then she is likely a Marans mix. If it came from a place where only pure breeds were kept together, then yes, I'd say blue Marans is the answer.
He's a barnyard mix, and they are just as good as any pure breed. I can't see any signs that indicate a pure breed was one of his parents. The parents were probably mixed breeds themselves.
Crossing a barred male onto a solid colored female won't give sex links. All the chicks will be barred.
Crossing a solid colored male onto a barred female will give sex links, due to the genetics of barring. A female can only pass her barring gene on to sons, not daughters. If the male is...
The combs and wattles say male, but I'm not 100% certain because their plumage coloring is even and not patchy.
If they are cockerels, they will get male specific feathering at 12 to 13 weeks. Post back if it's not obvious by then.
The chicks will still look good. They'll be mostly black with silver leakage, so may not fit a standard color variety, but that doesn't matter unless it is planned to show them.
Silkies can have hidden color genes, so you can get surprises.
They are pretty. The chicks should be sex linked. Female offspring will be gold partridge, males will be silver with gold leakage on the shoulders. I'm not sure if the penciling will carry over to the female chicks.
Yes. In old times some breeds were specifically bred for short legs because people thought they did less damage while scratching around in gardens. I don't know if there's any truth to that. Maybe.
Yes. That could be in the mix, but they have such high carried tails that I didn't think of it. Sometimes short legs just turn up, especially when bantams are mixed with standard size breeds.