My mother in law did sidestroke through her first triathlon- and beyond. My first race I was so amped I ended up breaststroking, carefully. It took a few before I could really get a good rhythm. You do what you have to, but backstroke is definitely a rough choice. Sidestroke sounds better. Lots of breaststroking happens around buoys and when swimming into the sun.

I like the plan to get used to freestyle. I use the counting technique when I'm tired of running but want to keep going - it's more useful than "to that landmark" for me for some reason. I use it for swimming in the pool as a "swim hard for X strokes" thing, too.

Good luck!! You've got plenty of time to work on it.