Hey Imeric, chill a little bit could you?
You are getting very close to being happy with MC for recording TV, and your observations and suggestions have both been helpful, and are getting a lot of attention. That is all good, but every little new thing you discover that doesn't work exactly the way you wish is "critical". Sorry to be negative, but it is getting a little old.
On question 1: First, I am using the JTV recording format, so we may have different experiences. Second, I very rarely even see a "lockup" which is usually just a long time waiting for MC to finish what it is doing anyway, and almost never see a crash. Usually only when I have been screwing around with MC and/or the HTPC.
Anyway, when I have seen a lockup/crash, MC has always (from memory, because I'm not going to test a crash) already created a record in the library, so I can play it like any other recording. Usually when I restart the MC User Interface, there are now two records for the one recording, the second with a "(1)" suffix, as MC will restart recording when the MC Server restarts, based on the Recording Rules and a still running program.
If you weren't recording a program, but were just Time Shifting and watching it, then yes, you will need to use Windows Explorer to go looking for the Time Shifting files, if you want to finish watching the part you hadn't seen. If that happens to me, I restart MC, do a One Time recording of the rest of the program I was watching, so I know that part will be saved, then I find the Time Shifting files and watch that, then watch the ongoing recording.
If you are using the TS file recording format, you could end up with a corrupt TS file for the first part of the recording, which may or may not be recoverable. Crashes do that sort of thing to files that are being written to.
On question 2: When I have seen any lockup or crash, from memory at least some of the time the MC Server (which is a service) is still running in the background, and so it will continue to record scheduled programs even without the MC User Interface running. In those cases only the MC User Interface has crashed, and as I said earlier, if left to it own devices, sometimes it will recover even though Windows thinks it has crashed.
In fact I have seen unrecoverable "crashes" (a couple) where the MC Server is happily continuing the recording, which I check by looking at the files, and so I leave fixing the MC lockup up until after the current recording is complete, and then I do a recovery. This has worked well.
However, if the MC Server has actually crashed, then there are Windows functions to restart it. I am using Windows 7, but I'm sure the same functions will be in Windows 10.
Start the Services application in Windows. You will need to be an Administrator, or run it as an Administrator to make the changes. Find the "JRiver Media Center 21 Service". Open the service Properties (double click or right click+ properties). Select the Recovery tab. Set how you would like MC Server to recover. You will see that there are settings for First, Second and Subsequent Failures. If you want MC to always try to recover, set them all to "Restart the Service". Then set the "Reset fail count" to 1 day, and the "Restart service after" to a reasonable time. 1 minute may be fine, lots of services are set to 2 minutes. Experiment with the time if you need to. Read up on the other settings to see if you want to modify them.
Jobs done. Not hard. Enjoy!