some questions

Selam aleykum
I have some questions I would like an answer on. One of teh two also comes with a lot of sub-questions. I have searched a bit by myself, but I don't really know what word querys to search and haven't pulled up anything reliable so far.

Today at jamaat, the Imam prayed both salaat al-maghrib and salaat al-esha together (at the time of Maghrib). I was told that this is because The time of esha is to late (past midnight).
So my questions:

1.1 Is it permissible to do this? I was told there are fatwa's about this. But is there any hadeeth that gives authority for praying Esha before it's time like this? I mean in order to pray a prayer before it's designated time -something that normally is forbidden- they need good proof's right? They can't just make something which is normally forbidden permissable based on ithijaat or analogy right?

1.2. If it is permissible, is it recommended to do this, or is it still better to pray salaat al-esha at esha?

1.3. Why would this rule only apply once Esha comes after midnight? I mean, our 24-based clock is completely arbitrary. The middle of the night is actually at 1h29 (Zohar is at 1:44, which is 15 minutes after midday. So the middle of the night would be more or 12 hours after midday.)

While asking if this is based on hadeeth, the brother replied: well first off all we shouldn't be here in the first place but do hijrah to an islamic country. Which brings me to my next set of questions

2.1. Is hijrah mandatory for muslims in the west? He made it sound like it, he didn't use the words sunnah, farz nor wajib, but simply said "should" which is a bit ambiguous. He said the only exception is for scholars who give dawah. Sounds weird if you ask me.

2.2 Again, is there any hadeeth or ayath that this is based upon?

2.3. What is an Islamic country. I mean there's no more righteous caliphate, and almost every "Islamic" country has at least some rules in there law that are questionable.