Nothing wrong with Krylon—I've used it myself with fine results.
So you have a lacquer or enamel over an acrylic, over enamel. Hopefully, the future is a nice, thick coat.
Check the Krylon. Does it say that the material is a lacquer? (This is likely—artists don't like fixatives that shrink, and lacquer shrinks much less than any polymer.) If the Krylon tells you what solvents it contains, use one of those to remove the matt over the decals. The difficulty is that if the solvent is an alcohol, you may dissolve the Future, too. You will probably loose the decal, but that's hard to tell.
If a solvent is not listed, try on a cotton swab, in this order: methyl alcohol (Everclear), isopropyl alcohol, Windex, MEK, and lacquer thinner. Test a small area, first. You may have to let the alcohols and Widex sit on the surface for a moment, but don't do that with MEK or lacquer thinner. Use very gentle pressure and work on small areas, trying not to affect adjacent areas.
Hope this helps…