Failure rate seems to be higher for the airnav green sticks compared to other SDRs.
That’s anecdotal from reading from people with issues.
It helps a bit to remove the plastic casing so it doesn’t run quite as hot, it has a very small PCB and can’t dissipate the heat well.
This is another options that’s similar to the FA Pro stick: https://aliexpress.com/item/1005005466363998.html
Unless your loft is extremely hard to access, i’d try moving the setup there once you have it running and receiving.
There is really no reason not to try as it’s almost guaranteed to provide a more well rounded reception in all directions compared to a window.
Doing FA + FR24 is probably easiest using https://adsb.im/
Other options will require using the command line. (not that that’s a bad thing but it is quite a few extra steps)
I’m not sure there is really much popular software for the pi4 that would require 4 GB of memory, 2 GB should be fine. But that’s a small price diff.