Ah, so basically, i should be relying more on my AD and less on my AP after the stun. I'm still used to playing as Ryze, I guess.
Not sure what you mean by this, could you rephrase it please?

My biggest trouble seems to be not making a decision soon enough as to whether to move forward or fall back, as Taric is slow as fuck.
Myahh i get that, you're afraid of burning spells only for your ad or team not to do anything on it. If your AD is good he'll know to follow your lead, if not just instruct him to go all in after you do and the moment you see an opening go balls deep.