#1 definitely sounds like a pager. It will sound better if you listen in FM. If you have another receiver, hunt around 150.8 - 162 MHz and see if you can find one that's the same. Hopefully this (and #2) are just images in your receiver. If not, the FAA will be upset.
I've heard #2 millions of times before. Don't know what it is, but we've got this thing around here. Listening to it right now on 452.29375 MHz. It ID'd (every 15 mins) and its callsign is KNHV797, which is Suburban Taxi here in Minneapolis/Bloomington, MN. The FCC lists them at 452.3000 MHz, so perhaps the FCC isn't up to date (e.g. recent upgrade) or the RTL-SDR is off frequency.
Was #3 on 205 kHz? If so, might be some PLC or other data monitoring system.
And paging is still in use. Saw someone carrying a Motorola pager just a couple of months ago, of the same type I used to carry 10+ years ago. Could feel my blood pressure rise just looking at it.