Can't answer the last one(probably yes), but the first question, probably not. Mainly because they had no reason to think the people searched had drugs to begin with, and the focus of their investigation certainly wasn't anything drug related, but an armed maniac on the loose. I'm not an expert on that, so I'm probably wrong.
See, I think is an interesting question.
Let's say that the police searching a house saw some drugs that had been left on the kitchen counter. The police have a right to seize or otherwise act on any evidence of a crime left in plain view, providing they were legally in the position that brought said evidence into view. So the question would hinge on whether they were in the house legally or not, not what purpose they were actually in the house for.
Any such case would depend on whether the house-to-house search was "reasonable" or not, with very little legal guidance on what reasonable is in this context. Also on whether the police were invited in (waving any fourth amendment rights) or not.
It's most likely just a hypothetical, but a fun one to pick over.
For the second one, it would be when(if?) he regains consciousness.
I'm less certain about this one.
From a prosecution point of view, it seems extremely unlikely that any case against the man will be based on his testimony. Not reading him his rights will make any such testimony inadmissible, but not unusable. If the authorities were more concerned about gathering intelligence than evidence then they might choose to question him for a while without letting him have access to legal representation.
In fact, current case law allows for interrogation done for purposes of public safety (such as determining if there are more people acting with the brothers, or if there might be bombs or other materials hidden somewhere)
can be admitted despite Miranda. My guess would have to be that there will be a period of such questioning before he is read his rights and the criminal prosecution properly begins.
What I'm less sure about is whether such questioning is really required given it's almost a definite PR hit against the authorities (even if it is legal, makes sense and doesn't violate any rights). I can see potential advantages, but I'm not 100% sure either way.