You describe very well why mono and poly are generally incompatible relationship preferences. Your way of loving someone romantically doesn't match his way of loving, and you feel hurt and unloved by his tinder dating and being affectionate toward this girl he has just met. I feel that this might be the biggest obstacle for a happy relationship.

But if you still want to try (and I understand why you'd want to try), focus more on what you'd need from him to feel loved than how he expresses his love for other people. You will have to focus on your and his relationship, not on his other dates, no comparisons. If you feel you get less, ask for what you need more of, and be very specific. (The Jealousy Workbook might be helpful).

I only want to learn to be a better partner for the person that I love

Being a better partner for someone goes through being a better partner for yourself .. by being attentive to your own needs and asking for the things you need to feel more loved and secure in this relationship.