i am thinking that maybe i just need to store the length in frames of each of the steps, then calculate based on that length how long the increase should be for each it in order to get to 100%, this way all would be equal length.

blendP += own_step * speed * time_step;
blendP %= 100;

is there a way to know how many frames there are in a animation? this way i would not need to store anything. i could calculate it on the fly. ent_frames just gives the total num of frames