Since you are actually using the laptop on battery, don’t set a charging limit. That is really for people that are leaving it plugged in 24/7, because sitting at 100% for long periods of time is bad for the battery. Use it, wear it out, and replace it.
And since you were seeing such low reported capacity, I would go ahead and discharge, charge, and check again (after removing the charge limit). Contact support if it’s still under 80%.
If your battery is going bad, the 12th gen beta BIOS supports the larger replacement battery, which may be worth the upgrade anyway: 12th Gen Intel Core BIOS 3.08 Beta Release
Although I get more than 3.5 hours from my 11th gen doing music production work, so you might also have some background app or expansion card or configuration problem causing power drain.