Itinerary set-now some concerns...

I just booked my 2 europe flights which were more expensive now since I had to wait until I got paid! But still cheaper than the train and better than the 15 hours..yikes. 45 euros each ticket.
I have yet to book my train from amsterdam and was wondering when I should book to get my cheap morning ticket at 39 eur and also the hostel i booked in paris was supposed to open in january and hasn't opened yet. I emailed booking people but now I am concerned. I am not going until may, and hope they will be open anyone have a suggestion? I want to stay there if possible since it will be brand new and all...