1. Yes, makes sense.
2. Check this timeline to get an idea:
http://www.immigrationboards.com/uk-tie ... 60823.html
2.a current employer HR generally check renewals/further processing around 1-3 months, so they may ask when you plan to apply for ILR so they can support your application, etc. Yes, they will know if you don't approach them for ILR until your current visa runs out. They can't do anything but expect you to provide notice if you plan to resign, but without valid visa they won't allow you to work after visa expiry.
2.b. if your current visa expires before your new application gets rejected, then you'll have very limited time to get things in order. You'll have couple of weeks I think to file admin review (AR) if you think ukvi did some mistake. While AR is going on you could file a new application with another employer if you have a different offer. As long as you file in time, you'll be ok but it's going to be stressful & messy and if things go south you may have to go back to your home country.
In this pandemic, it's best to stick to current employer, get ILR sorted and once you have it's much better to change jobs. Just my personal opinion btw. If super priority application comes back then you can definitely try your luck with new offer but otherwise you need to think hard if it's worth the risk or not.
My advice is based on personal research/experience, so pls check relevant UKVI sources.