I'm playing since about 3 month and will try to answer your questions.
1) How long does it take to reach lvl 50?
I'm playing about ~2 hours every day in average and after around 75 days I'm level 42 with my main class. I also leveled a second class to level 30, a crafter at 40 and a gatherer at 28. I progress a bit slowly, but thinks like changing the colour of my chocobo, crafting new items and selling them on the market etc. make a lot of fun. I think when you try to level fast, you can reach level 50 in about 3-4 weeks.
2) Can u tell me about the PVP Arenas?
I just tried the 4 vs 4 Pvp. I'm not really into it, so someone else should help you out here.
3) END GAME CONTENT? I want an MMO to keep playing for a while. Maybe like a year or something.
There is a lot of endgame contend. I didn't reach level 50 yet, but what I could see at my free company, they are busy since month.
4) Is it worth the 15$ monthly fee and will it always make me want to come back to it?
It is. There are regular updates with new content und you get entertained quite well for your money.
5) Does the game feel alive? I know there are 2.5 Million players, but is it easy to find dungeon/raid participants easily?
You can see players at every region. There are no points with hundrets of players online, but as it is a huge world, there are several spots with smaller groups. So yes, it feels alive. As a tank or healer, you'll find a group for dungeons or raids nearly immediately. As a damage dealer, you wait between 15 und 45 minutes. Its much easier with a guild :)
