I also had many problems with the decals for this kit, and gave up after applying half the decals which cracked in many places and I was unable to get to conform to the body contours.
Earlier this year Shunko Decals released a replacement decal sheet for this kit, which provides all markings except the large color areas, which you must paint. HobbyLink Japan has this sheet currently in stock:
http://hlj.com/product/SHKD292
I bought one of these sheets but have not yet tried tackling the project, as not sure how to remove the decals I already applied without damaging the paint (I used Tamiya TS spray paint decanted and airbrushed), so I can't tell you how well the Shunko decals work. I found some craft acrylic paints in an arts & crafts chain store that appear in the bottle to be somewhat similar to the colors needed.
Good luck, and if you do try using these decals, please post your results for the rest of us!
Cameron