Do you have a couple of 8gb USB flashdrives that can be used?
I would try this:
1. On the MacBook (as it is now), create a new user account. Give it a simple name, such as "Administrator", and the password of your choice.
2. Connect the first flashdrive
3. Use CarbonCopyCloner to create a "selective clone" to the flashdrive. By "selective clone", go into CCC's "left menu" and chose NOT to copy your actual user account (which probably has too much "stuff" to fit onto the flashdrive). The same for Applications -- you can go in and DE-select everything except the essential Apple apps.
The idea is to create a bootable but "slimmed down" copy of your internal drive so that it will fit onto the first USB drive.
4. When done, DO A TEST BOOT of the new flashdrive by rebooting with the option key held down until startup manager appears, then select the flashdrive and try to boot from it.
Does this work?
If so, next step:
1. You will need to get a copy of the Snow Leopard DVD onto the -other- flashdrive. If you have access to another Mac that has a DVD drive that will read the DVD, use that Mac to copy the contents from the DVD to the second flashdrive.
(NOTE: if you do NOT have access to another Mac, there are "alternative download methods" by which to obtain a copy of the 10.6 DVD dmg, but you will have to seek them out and discover them on your own...)
2. Now, boot the MacBook from the FIRST flashdrive to your new "Administrator" account.
3. Use Disk Utility to re-initialize the internal drive. Use the secure erase if you wish.
4. When that's done, connect the SECOND flash drive with 10.6 on it.
5. Try running the 10.6 installer, and "aim it" at the internal drive.
6. Can you get a fresh copy of 10.6 installed onto the internal this way?