What you have there looks like it would work. It's pretty similar to what I did with a sour mash/ambient ferment beer a while back. I'd be more worried about a too-small lacto pitch than a too-large ringwood pitch. When you say "proper temp", do you mean 100+ for the lacto? It will thrive there. If not, you might want to give it more than a week, as lacto reproduces more slowly at lower temps.
As far as fermentation products, if you pitch commercial lacto (lactobacillus d.), then yes- you'll only get lactic acid and CO2. If you use bottle dregs, such as Phantome, you'll get a mix of lactic acid producers, some of which can produce alcohol (and other compounds as well).
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