If it was just a scratched defroster line, you can buy repair kits which are essentially paint with lots of metal particles in it. However, I haven't heard of any way to fix a broken connector. I hate to say it, but how much is a new rear window?
Blower motor resistor
It sounds like the blower motor resistor has a couple of burnt out connections. The resister is on the front-top of the blower motor unit. You can get at it by removing your glovebox. If you pull it out, you'll see that it's got a few coils of wire that act as resistors (for each fan speed setting)...if these coils are broken or corroded, the corresponding setting on your fan switch won't work. Replacement is the best way to fix the problem. (or, if you are electronically inclined, I'm sure you could figure out a way to wire in some big replacement resistors...if you knew the original resistance settings.
I have fixed the lugs on rear defroster setups at work.It is fixable,although its not easy.
I repair them at work with a good quality soldering iron.
I use a portable Snap-on one,but a good adjustable temp one from an electronics store will work.
BUT make sure that the temp is adjustable up to like 800 or so.
I know solder melts at a much lower temp,BUT you need that higher temp rating to get that large puddle of solder to gel.
First clean the points of contact and get a decent 60/40 rosin core solder to use.
Heres a link to a on-line soldering iron store for reference. link
If money is tight the SP-80 will do,but if you can afford a lil more I'd suggest the weller wlc100