Dualboot(Windows, OpenBSD) * FDE

[beiroot]

As my Toshiba netbook is sweating its ass off trying to render any webpage under OpenBSD, I decided to switch to something more powerful. I'll be using Lenovo IdeaPad z710. It already has Windows 7 installed with such partitions (picure 2.PNG). The task is to install openbsd without reinstalling windows. I organized some space between the windows partitions, so that OBSD can be on the primary, not on an extended partition (seen in documentation).

My goals are
1. dualboot
2. fde (windows is not encrypted now)

Scenario minimum is nr 1 only. Scenario maximum is 1 and 2.
Now I think I know this can be achieved because I browsed through the forum and looked for some info online, but I just wanted to make sure I have the decent understanding of what my options are.

Regarding dual boot: (picture nr 1.PNG)
1. I could install OpenBSD on fdisk partition nr 3, leave MBR as is and add necessary lines to Windows BCD. Am I correct?
2. I could install OpenBSD on fdisk partition nr 3 and tell MBR that it should boot from this partition. Then install GRUB and add Windows. Am I correct?
...

Regarding encryption:
1. I could install obsd using softraid encryption and use bitlocker on windows. Then I guess depending on the bootloader I choose, I need to provide password in different place? I've read this thread

2. Can I use third party software like Truecrypt, Veracrypt etc take care of the FDE and on-place password typing? I know Truecrypt doesn't support dualboot unless windows BCD is used, right? Other issues is, whether third-party soft will see partitions properly?

Thank you very much for any information/suggestions you have.