You are young with a degree with a great job, why do you want to create a hole in your CV to play tournaments? IMO, keep grinding your job, soon enough you will be making money to travel around Europe and the world and gather experiences
Anyway, answers to your questions:
1. If you want to be around the lively areas (i.e St Julians/Sliema), 300-350 will probably not be enough. With 400-500 you should find an ok place and higher than that the sky is the limit obviously. Now if you share an apartment with other poker players then the cost depends I guess.
2. No idea.
3. Without employment, very hard.
4. Local girls not that easy but you should not have a problem getting laid if that's your concern. This is a tourist place and also a lot of expats from all around the world are working here.
Gl...