Excuse my ignorance, I don’t have any bio-magnets myself, But
How do you mean? You haven’t said how the other magent is/was better? Only that you xG3s are uncomfortable.
Could it be the your previous one was simply installed better? Was it installed in the same location?
If the syringe method hasn’t worked for you, have you considered removing the xG3s and having a scalpel install install.
From what I have heard, Brian Decker is a skilled BodyMod artist, so If he also installed the magnet, that could be a discerning factor.
You mentioned “We couldn’t figure it out.” who is we? Was it an experienced bodymod / piercer / doctor that did the install?
What form factor was the Brian Decker one? Are you comparing apples with oranges?
Was it safe? did it start to disintergrate? Do you still have it installed? If not, why did you remove it?
You installed it 10 days ago, Sorry I can’t help you with the expected healing time, But I would say, the xG3 needle is large and the fingers have many nerves, Nerves can take some time to heal, so you may need to give it longer.
There are many other people that can give you their personal experienced advice.
The xG3 magnets I have seen other metion here on the forum all seem to be happy with thier choice
Here is some Magnet 
candy if you haven’t seen it
This may also be of interest to you
In the mean time:
Maybe some pain killers to take the edge of 
At the end of the day, If they are too uncomfortable, I would suggest you remove them, or just one, until the other heals, so that you are not left “incapacitated” with 2, then reinstall the other one later.
( Personally I wouldn’t )
Let us know what you choose