I think I might have an engine problem... :(

I've never claimed to be a motor expert, but I'm hearing a couple things that are concerning me. I agree that it sounds like it is running rich, possibly very rich. Have you had the plugs out of it? Do they look like it has been running rich?

My concern is that it is making more noise as time goes on. I would pull the dipstick and see if it smells like gas. Like I said, I am by no means a motor expert, but I have heard of cars running WAY rich actually washing the cylinder walls. You've stated that you are getting excessive blow by when it is cold. I would check to make sure you aren't getting raw gas blowing by and diluting your oil. Might explain why the noises are getting worse as time goes on since your last oil change. I have heard of instances of where that got so bad that they hurt their motor.

If that is it, I would think you would want to get the oil changed and adjust the carb to stop it early before it does any damage. Correct me if I'm wrong, but don't rich running engines run cooler? Might explain the lower operating temps too.