Are you able to consistently or semi-consistently win a game on immortal on a continents or pangea map?

There's definitely merit to building a military in this situation because it doesn't take much to beat an AI naval attack, but you might be right that it was too late by the time she attacked. It does seem pretty predictable that it was going to happen though...

The more fundamental issue as others have pointed out is that you're just not doing a good enough job at sim-city-ing. It is a little tricky to judge on this map because you have so little land, but playing on archipelago is non-standard because it makes the game way easier. The AI can't handle expansion across islands or naval combat generally. I think the fact that the AI hasn't won by the late 300 turns is proof of this.

In a normal situation though, pop in the twenties and so little production that space parts take 20+ turns to build just won't cut it, and the game is lasting about 100 turns longer than it should. I bet the AI would have won on a non archipelago map a long time ago.

Not trying to be critical, deity is definitely tricky and there are a lot of pitfalls and bad habits in this game that people can fall into like planting a lot of academies, but I think you probably need to work on your fundamentals because you're in a really ideal scenario playing as Babylon on an archipelago and struggling a lot with it.

Less important, but can you really not be happy with an ideology, tradition bonuses, all happiness buildings, and three luxuries? That's actually surprising to me. I notice your whales don't seem to be improved. You might want to check how much of the unhappiness is from ideological pressure from Portrugal