First I want to apologize if this comes across as harsh but it's not my intent but my intent is to see you on your bike riding and happy.
When someone does electrical work whilst the battery is still in and with the battery still attached to a turned on battery charger, I start to feel it will always end in tears and it is work outside of that persons comfort zone.
Before you spend another penny on anything may I humbly suggest, you hire a van for a day, load the bike into the van and take it as it is to either taffy or jaws.
The blackbird has very few problems but you seem to have got your self in a right pickle. These two gents will fix the bike properly, get it and you back on the road and will never rip you off
Given what's happened it will probably be the best use of your time and money and see the positives of blackbird ownership return and the problems be a thing if the past