Did the plagues represent anything in particular?

A reasonable number of scholars think that each plague was a confrontation against a specific Egyptian god. In the end the plagues demonstrate Yahweh as greater in power to these false or lesser gods. Not only are the people of Israel set free and Egypt judged but their gods revealed as weak. There doesn’t appear to be a parallel for the gnats/mosquitoes that we know of, but all the others are there. Even scholars that don’t think each one was against a specific god, believe that the sum of all the plagues was to show that Yahweh had power and the Egyptian pantheon of gods didn’t. Including Pharaoh who would have seen himself as a god-man. Numbers 33:4 also records that the Exodus was, in part at least, ‘a judgement on their gods’

What was the angel of death?

The angel of death, is something of a misnomer because that term isn’t actually in the text but the word ‘destroyer’ is, although it’s not unusual for angels to be described as carrying out punishment on God’s enemies. Either way, it’s death at the command of God (Ex 12:29).

Does the fact that it took a long time between the Moses going to the Pharaoh and the people being freed say anything about God?

Yes & no. It says a lot about Pharaoh and every other human. There were warnings, opportunities to relent, repeated chances to change course but Pharaoh’s heart is hard. The fact that it took time, I would argue shows that people are stubborn, we are slow to see, repent and obey and yet God can still be patient and give repeated chances to relent and avoid catastrophe.

A better question would be why is Pharaoh so willing to let his nation and people suffer? Why won’t he backdown? Why won’t we? We want to be in control and be lords and rulers. We don’t want to yield.

Why does God use, what I would imagine, are the devils weapons (sickness, suffering and death) in order to free people?

Firstly sickness, suffering & death aren’t the devil’s weapons as if they’re somehow outside of God. God allows people to undergo trial, or endure the consequences of life in a sinful world and ultimately to die God and certainly didn’t withhold even his own son from the effects of the curse.

Remember that a part of the Exodus is in overthrowing the Egyptian gods and revealing them as powerless to stop Yahweh. Of course, if one is going to bring judgement against something (a nation) or someone (Pharaoh), then you don’t really do that by giving them ice cream. But actually through this suffering, freedom results, through sacrifice lives are protected. Through trial, trust and faith is forged.

Did God like the Egyptian people? He seems not to by sending plagues and drowning loads of them but they were part of his creation too.

Well, don’t forget the Egyptians are the oppressors here, they’re actively keeping an entire people in slavery and captivity. As the world’s armies converged on Germany during the Second World War, would we say ‘why doesn’t God like the Germans?’ That’s beside the point but because Hitler had led them into great evil and they as a nation were complicit, the judgement of the world was on them as a nation. So it is with Egypt, the Pharaohs had led them into great evil and despite chances to repent, they refused and now it was the time for reckoning. We are today uncomfortable with the idea of judgement  but the Bible upholds the idea of national guilt. Israel itself often came under God’s judgement when kings led their nations astray. God wasn’t partisan in that regard. God upholds justice, the strong revelation of Exodus is that God is a God of liberation and frees those who are oppressed. Don’t miss that.

Why is death the ultimate punishment for sin?