1. Question: How did you manage that with COVID? Anyway ignoring that, don't try to address it. Yes it's not ideal to cram so much shadowing at once over a short period of time, but it's not a make-or-break sort of thing, so don't worry about it. Maybe you can address this during interviews if asked.
2. Depends- I know for a lot DO schools this is essentially a requirement, but for MD schools is different. If you've done a ton of shadowing over the past few weeks, I would not recommend asking a physician for a rec letter unless you're certain he/she will write you a very strong one. Four weeks is not enough time (unless it's something super intensive, which shadowing isn't) for someone to get to know you well enough for them to write a quality rec letter for you. Prioritize other letters over that one.
3. I would discourage against generally unless you have nothing else to speak about. ADCOMs know what shadowing is, that's great if you felt super involved and learned a lot but at the end of the day there's not a whole lot you can do as a premed student while shadowing so don't try to play off your shadowing as something that it isn't, ADCOMS will see right through that.
Just my $0.02, take it with a grain of salt.