The only way to test the batteries: xDrip+ Android app.
Now i grind down the whole body to the batteries and make a full seal layer over both batteries with epoxy after replacement. Then it’s easy to unglue it with a screwdriver - stap into the edge of epoxy and move it up and down. The complete layer will plop away then.
Yes, i would prefer Energizer 389.
To remove the epoxy, simply take a tiny screwdriver and stab into it at the edge. Then move it up and down and you will see that the whole layer will unglue and comes up.
You should be able to solder a small wire on the broken piece. Maybe have to grind a little bit to see it.
I think if you are not able to successfully make a good contact with superglue only, conductive glue (wire glue) or silver will help as a second step after the superglue has dried. It is only needed for the upper (+) pole because the bottom (-) pole has a direct contact with the contact plate without superglue on it.
2K means 2 components epoxy. So you can use the gorilla suringe. The epoxy doesn't have contact with your skin.
All SR batteries are silver oxide. You mean the LR1120. They are not better because of less voltage (1.5V) and less capacity.
It's the slim model. You can check this by measuring it's height. 6mm - slim, 8mm - the old one (sandwich PCB).