You have one of the most desirable field guns made in the US. Obviously original condition is the biggest factor in valuation, but just being a small bore Elcee is beyond any question a great find.
I have to wonder why you feel a single trigger necessary. Double triggers are easy to learn and quite efficient. More so, in fact, than a single in my opinion.
I would advise that you do nothing to the gun that can't be reversed without trace. Do not modify it in any permanent way.
As to loads... Either/or is probably the most correct answer. Your little Elcee will likely prefer one over the other. Or not. Shoot what shoots best.