1) BML appears to be one of those Chinese phones that doesn't have any released specs until after they stop selling the phone. (It's a Froyo phone that ships with Android 4.2.2 - that much is documented.)
2) Unlike Windows, in Android (the OS itself), unused RAM is wasted RAM, so you should have about 90% RAM usage at all times. The memory manager is very good and will swap out the oldest run app that's not needed for something else if it needs space for something you want to run. Worry about storage, not memory.
As far as rooting, the only thing you'll need to find is an exploit that works. Once you get temporary root, use adb to install /system/bin/su (which is why Android phones aren't rooted out of the box - su is missing), /system/bin/busybox and install SuperSU.apk (from the Play store).
The trick is finding an exploit for an undocumented phone. Once you get root, even for one boot, it's just adb push whatever wherever. (And finding drivers that will let adb see the phone.)
If you're really adventurous, you can try programs like
Super One Click or
Kingo. But the standard "if you brick your phone, I'm not responsible" disclaimer applies. Doing it manually, the worst that can happen is an error message at the console, and you know you have to find a different exploit. And if you're familiar with the Linux command line, "can not access this directory" isn't going to scare you.
