Looks like I had my fuse tap in backwards as well, actually I see you have another going the other way was well.
You can get away with installing either way. The wire does not connect directly to either terminal, so even backwards, the power still goes through a fuse to reach the wire.
One way the tap is before the first fuse and both fuses feed from the bus. The other way the tap is after the original fuse, and the added fuse (and it's load) are added to the the first fuse.
In both cases power goes through the same original fuse to get from the bus to the original load, so no problem there.
It just means the original fuse comes closer to blowing depending on how much the added load is. So it's not ideal but it's not unsafe (as long as you don't change the original fuse to a higher rating) and it also doesn't provide any path to backfeed power into the original circuit or for anything to get around the fuses or anything like that.
Just don't increase the size of the original fuse to compensate, because that would mean that if there was a short or bad component anywhere on the original circuit, and the added circuit didn't happen to be actually adding it's additional load right then, then the fuse would not blow when it should.
There are several unpopulated fuse locations where you can do pretty much whatever you want. You can just look in the socket and see the bus terminal on one side and no terminal at all on the other side. You can test with a meter and see that the one side has power. And with no physical connection on the other side, you don't have to worry about the capacity of any existing wiring. You can install it whichever way fits and just put 2 of the same size fuse, of whatever size you want. The power will go from the bus through one fuse, through the other fuse, to your new load, without going anywhere else.
Maybe none of those unpopulated no-connection spots are on only exactly during ignition. But it sounds like you are using this either just as a sense wire or only to add a pretty small load, so maybe adding the load to the original fuse is no problem. If the original fuse is say 10A, and the original load is only say 5A, and you are only adding say 2A, then 7A is still fine for a 10A circuit.