Texting agreements sounds like 'permission'
Your negative feelings are yours to deal with, not your partner's to tiptoe around/avoid triggering. I can't imagine telling those I love how much they can or can't do something that they want to do (and enjoy), and I sure as hell can't imagine being okay with one of them trying to control me via emotional leverage. Letting him know how his actions make you feel, that's one thing, but setting up rules for his behavior? That sounds control-y.
Your partner is experiencing NRE, which is awesome. Try to be happy for him, experience some compersion; share in his excitement and joy. This kind of thinking will not only make the jealousy easier to wipe away, but will open the door for some awesome emotional synergy with your partner/s.
Me: Straight male, anarchistic polyamorist, hate labels
N: Straight male, best friend throughout childhood
M: Bisexual female, introduced her to poly
C: Bisexual female, 'girlfriend' of N before poly encouraged de-labeling
A: Straight female, newest in my life
I love them all.