Future over Tamiya gloss?

You didn't state whether the Tamiya gloss black is acrylic or enamel. Makes a big difference.

How long did you let the paint cure before overcoating? Tamiya gloss colors take longer to cure than flats, up to twice as long under some conditions. That would put your minimum "safe" cure time at about forty-eight hours.

You said you wiped down with alcohol before applying Future. What alcohol at what concentration? Tamiya acrylic paints are highly soluble in methyl, ethyl, and 90% isopropyl.

Fish-eye and beading are caused by surface contamination. Both acrylic and enamel gloss colors in the Tamiya line often contain a silicone additive as a gloss enhancer. That's why sanding the surface removed the problem. 

If the black is enamel, scrub the surface with methyl, ethyl, or 90% isopropyl on a soft cloth, or you can use a surfactant cleaner like 409 or Simple Green (the latter needs to be rinsed off). I the black is acrylic, sanding is your best option.

Note also that applying Future in multiple thin coats may help. Also, when applied in a heavy coat, Future often fish-eyes horribly—half an hour later it's glass smooth.

Man! I love our chemists! 

I'm not sure of acrylic Vs emanel. The black is TS-14 and the clear is TS-13. The warning says it contains acetone, isobutyl acetate, Methyl isobuytyl ketone, and may contain mineral spirits. I know it appears to dry quickly and stinks quite a bit. It behaives a lot like laquer.

I used 70% Iso alcohol in the wipe down.

Should I clean with simple green, decal then future or use Tamiya clear, let dry, 2000 grit sand future ,decal, then apply more future?

The decals are from DMC, a Dutch company.   Thanks, Greg

Its solvent composition is consistent with modern lacquer.

Seventy percent isopropyl is almost as likely to add contaminants to the surface as remove them. That dilution is generally locally produced by diluting 90%+ with local tap water—fine for rubbing alcohol on human skin, but not so good for models!

Clean with Simple Green, rinse, 90% isopropyl wipe. What you do after that is your preference,  either Tamiya clear or Future. The advantage to  using Future throughout is that it's one less component in the system, and is friendly to most decals. I also find it easier to use than Tamiya clear.

Don't know anything about DMC decals.

Good luck!