As long as the power bank is a USB standards compliant power bank, then it should not harm your iPad.
Note however that even though a power bank or charger might be able to deliver for example 30W (or even more) - it doesn't mean that the iPad will be able to take advantage of that for faster charging. USB-standards compliant power banks and chargers only ...
As you have the iMac on a UPS, you could use the power consumption readout that is usually available on a UPS. I.e. if the power draw is above a few watts, the computer is on - if it's not, the computer is off.
Another option is simply to connect a cabled, USB mouse/keyboard instead of the Bluetooth. As having a malfunctioning UPS at the exact same time ...
I think it's unlikely that your total electricity bill went up significantly because of this. A battery is just an "energy container": the energy it contains came from your wall socket.
If the battery won't hold charge, then the Mac is just using the electricity it needs to run.
If the battery will hold charge, then the Mac is using the electricity it ...
I support @Fasani 's answer.
After tests of daisy-chaining newly bought MacBook Pro (model A1990 EMC 3215) with ASUSPRO (b9440UA) I concluded that you can't daisy chain 20V USB-C power supply, however you try.
MacBook Pro is very aggressive in getting whatever power is available to it, so it will eagerly use 5V if that is all it can get. Of course, ...
I would suspect something is wrong with the center pin of either your MacBook or your power adapter. In this Apple support document it is described that a missing contact on the center pin may cause the adapter not to charge the computer. This answer elaborates on the pin configuration that is necessary to charge the computer further.
As the Apple support ...
A while back Apple introduced something called "Power Nap."
Basically your Mac will still do some background tasks while asleep. I am guessing that this might be what is going on.
System Preferences > Energy Saver
and look for "Enable Power Nap while on battery power."
I would guess that it is checked, un-check it and see if that helps.
I do not think that that can happen: when you look carefully at the lightning connector you will see that the metal body of your mac will touch the upperside of the lightning connector which is one band only and not one of the contacts that are on the sides.
Troubleshooting is a process of elimination and often requires patience.
In this situation, if you've already reset the SMC (and it may be worth doing again, ensuring you've followed the correct steps for your model), you'd normally want to isolate the different components by testing them separately (e.g. testing the battery in another 2012 MBP, testing ...
You haven't tried checking the power adapter. Power adapters get damaged so before being concerned about the battery. It's best to check wether the power cable is working by either plugging it into another similar MacBook Pro(make sure it's the exact model) or by reaching Apple.