Your hostel is on the eastern end of central Paris, not far from Pere Lachaise Cemetery but some distance from any other sightseeing attractions you might want to visit. However, it's only about five blocks from the Porte de Bagnolet Metro station on Line 3. From there you can take the Metro anywhere in central Paris and do all the sightseeing you want in the time you have.
It looks like a nice neighborhood with high-rise buildings and good sidewalks, but not as "charming" as some of the more central -- and more expensive -- areas. If you have the energy to move around on the Metro, and maybe buses, you should do fine.
Whether to spend one of your three days going to Disney is your choice. I haven't been there and wouldn't be interested, but that's me and you're you. The RER "A" line goes there, and you can connect to that by Metro. Have a wonderful trip!