First, the capitalization…
I sort of understand why king is capitalized. It shouldn’t be, but it’s not nonsensical to write it that way. Why capitalize blacksmith, though?
Being the king’s personal blacksmith is hard work. It would be easier if you knew your son was not in chains.
Note the apostrophe in king’s! I find it highly unlikely that there are multiple kings who share one blacksmith, and if there were, you’d still need an apostrophe, just after the s instead of before.
I’m not sure what was intended with the second sentence. Is it that the blacksmith’s son is in chains, and his job would be easier to deal with if this were not so? Is it that he doesn’t know whether his son is in chains or not? Would his job be easier if his son was in chains but he didn’t know about it? At any rate, each of these possibilities would be best expressed by slightly different word choices, etc., and I suspect the words that are there are not expressing the writer’s intended meaning.