I took the liberty of adding names for your partner and metamour, for clarity.
This does sound complicated, the continuation of Sam and Faline's relationship, or at least feelings for each other, and the way Sam has gone about managing to share his time between you and Faline, and his tendency to promise something (no sex, no other intimate sexual behaviors) but then not doing that, breaking his promises.
As for your main question, about needing more resources-- you can do searches here for specific terms-- cheating, negotiating, lying, new to poly, etc. There are also quite a few good books on polyamory to look into. The most popular are Opening Up, and Polysecure. They will address your concerns.