thats strange, my boot menu has 2 kernel selections for pop os, the current one and one that is the previous running kernel. if a pop os update breaks my system i can just boot from the other kernel image. which has only happened once in 5 years. but was able to wait for pop to push fixes etc and then dist upgrade.
since you dont seem to have that option, you may need to boot from live usb and investigate further.
when you try to boot into it what happens?
yeah i was just thinking this the other day. i have alot of packages on my linux boot. i run mysql,postgres all kinds of stuff, many python versions, still fast as the first day i installed it. windows on the other hand starts bogging down fast. i keep my windows boot withonly the bare minimum of things and turn off almost everything from the start up, woth the hopes of keeping it useable.