Yeah lemon juice is fine, due to it's acidity it would already transform freebase alkaloids into salt form.
I'd rather make a whole brew with rue or caapi though, instead of just dissolve the alkaloids.. I don't have any real data to back this up except my own experience but it seems to me there is something in the complex mix of alkaloids present in whole brews but not extractions (even when extracts are redissolved) that aids the absorption of alkaloids.
Also, im not sure how your 10x extract was made, no idea how potent it is.. Thats why I much preffer extracting myself (or taking whole brews I make) than getting someone's supposed concentrated extract.
But in case all you have is the extract, then yeah I'd still try dissolving it all in some lemon juice and see how that goes. Hopefully its a good experience.
And lastly.. Careful what you wish for
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Be well!