I'd figure out a way to flare that spacer just a bit so it's a near press fit. Less to worry about. You'd only need to flare the ends of it

"Accuracy is lacking" is kind of vague. How does the rifle shoot unsuppressed? What are the group sizes at what range? Are you using the same ammunition suppressed vs unsuppressed? If you want a tack driver with a can, it needs to be a tack driver without one as well

Wow, that's both impressive and terrifying at the same time....

Mercury will dissolve lead as well....though I'm unsure how it does with aluminum