I had to strip off all the decals to a project I did a while back because the adhesive had turned amber. Bad because the model was gloss white! (1/24 scale Peterbilt Wrecker). As I removed each decal and got them off the backing paper, I had to rub off the adhesive with my fingers and a soft paint brush until the carrier film showed clear. To get the decals to stick to the model, I used Elmers glue thinned with water to a consistency of super skim milk. The model is over 20 years old now, and the decals are still on and look pristine. Placed at IPMS Nationals in Orlando to I might add.
I'm betting the tough time you had getting the decals off the paper was just that - the decals only. The adhesive never left the paper. Try the white glue solution, and use a setting solution if you feel you need it.
Tracy