Don't forget about the all-powerful neighbor bonus.
I would keep a German OPM next to you and grant him trade rights, (since you probably won't be trading much anyway due to infamy). That should give you a nice boost to tech.
I am mercantile -3 atm. i started at -2 as england so i stayed like that.
I got 5 merchants in all 4 of my CoTs but i don't gain much from trade yet.