Hi,
1. Who do they think they are that they dare threaten to send you out of the house, huh?
- Is this natural to say?
It's a bit stilted.
'Who do they think they are' already seems to convey the idea of 'daring', so the latter seems redundant.
The slight formality of 'that' contrasts oddly with the informality of 'huh'.
'Throw . . . out' seems more idiomatic here than 'send . . out'.
For a question like this, I hear 'eh?' more than 'huh?' But it would normally be omitted in other than very colloquial writing.
I suggest Who do they think they are, threatening to throw you out of the house?
Best wishes, Clive