I definitely think the two things can coexist. When he was physically away from you, on the date, it was new and scary, and jealousy thrives on uncertainty and fear. But when you saw him, saw his happiness and knew he was still with you, you felt his love for you and yours for him and knew that him being with someone else wasn't changing that, and compersion thrives on trust and love.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.