Make a slight change to your bottling routine that allows you to leave the spigot in the open position while transferring from the fermenter to said bucket. Don't do that.
(Luckily only a few ounces were lost)
If you want to improve this further throw a bag (or 2) of ice in the outside bucket. That's what I do, also the first water that comes off the chiller is still pretty warm so I would waste that before adding it to the outer bucket.
It might be a little yeasty, but with a wit, probably not a big deal. If you are really worried you could cold crash it overnight and speed up the clarification.
Yes, it has been done, in fact my LHBS sells funnels with filters for just this purpose. That being said, I don't filter when I transfer, I simply allow the trub to settle in the kettle for about 15-20 mins before transferring then pour carefully leaving about 80% of the trub in the kettle...
36-inches in a 42-inch frost line probably won't be a problem. But if it is really cold (<10 degrees F) you will be amazed at how quickly a small diameter pipe can freeze. You might want to add heated pipe wrap to the pipe that comes up to the surface in the garage, unless your permanent heat...