1) How do I determine if FileVault is enabled for my Macbook? Can I check this from recovery mode?
Because "You" would have had to intentionally enabled FileVault's Full Disk Encryption. If you do not remember ever doing anything like that, then chances are you did not.
2) I don't have access to another Mac at the moment. Will I still be able to copy out the files (and the iPhoto library) from the hard disk via a PC?
You would need to get 3rd party software for the Window system to read the HFS+ file systems used by OS X. If you obtain that Windows software, then it should be possible to put the Mac disk in an enclosure and read it.
3) My main concern is to retrieve my iPhoto photos. If I manage to get hold of the iPhoto library I believe the photos are usually copied and contained in the iPhoto library. How can the photos be accessed from a PC without iPhoto?
Pictures are standard JPG, TIFF or PNG files (most likely all JPG), which can be read by just about every modern computer today.
If your only choice is Windows, then it might be better to take your Mac to an Apple Store and get the Genius Bar to get it unlocked (make an appointment in advanced or you will have to wait a long time or come back).
In theory you should be able to reset the password from the Recovery Partition
<http://coolestguidesontheplanet.com/reset-forgotten-admin-password-mac-osx/>
<http://www.hongkiat.com/blog/reset-osx-user-account-password/>
<https://tidbits.com/article/14437>
<http://blog.macsales.com/17197-tech-tip-resetting-your-password-in-os-x-10-7-or- later>
<http://www.cnet.com/how-to/reset-bypass-password-mac-macbook/>
<http://www.macobserver.com/tmo/article/os-x-mavericks-how-to-easily-reset-ther-a dministrator-password>
<>http://blog.typpz.com/2012/10/20/how-to-reset-os-x-password-with-recovery-partit ion/
You should also be able to reset the admin password from Single User mode
<https://apple.stackexchange.com/questions/61905/how-can-i-reset-a-macs-password- from-single-user-mode>
<http://osxdaily.com/2011/04/25/change-admin-password-mac/>
<https://www.maketecheasier.com/reset-os-x-account/>
<http://hints.macworld.com/article.php?story=20080414140636495>
Once you have your admin password back, and can boot your system normally, you can use file sharing to transfer your pictures.