Here's some evidence for gentile obligation to follow Torah that I'm gonna be putting into a book on Acts 15. Sorry that this is just an outline and that I haven't gone through and fully explained each point. But it'll give you a taste of the magnitude of the rebuttal that exists for FFOZ's Divine Invitation position:
Evidences for Full Gentile Torah Obligation:
The Abrahamic Covenant promised that Abraham's seed would become a great nation. This was fulfilled by the Sinaitic Covenant. Exodus 19:5-6 shows us that the Sinaitic Covenant established the People of Israel as a nation. Jeremiah 31 shows us that the New Covenant is a reaffirmation of the national covenant (Sinaitic) because it makes explicit references to the nation and to the constituent Houses of the nation. Yeshua tells us that His blood is the blood of the New Covenant. Therefore, partners in the New Covenant are members of the nation of Israel.
Epistrepho: Peter uses this term interchangeably with "immersion" (Acts 2:38 and 3:19) which shows that Peter saw Cornelius' immersion as a rite of initiation into the Israelite religion (Acts 10,11) and also that Luke and James saw the "conversion" of the gentiles (Acts 15:3, 19) in the same way.
Kahal, Ekklesia, and the Expression "Day of the Kahal" as Shavuot: The latter expression refers to Israel (Dt 9:10; 10:4; 18:16; 5:22). The Day of the Kahal refers to Shavuot when Torah was given. Gentiles are included in the New Covenant Shavuot (Acts 11). Stephen applies ekklesia to Israel in Acts 7:38. Ekklesia is the word for Church and it comes from the Hebrew word for the political gathering of Israel (Kahal).
Covenanted (proselyte) and Non-Covenanted (paroikos) Dichotomy of Gerim (LXX). Ephesians 2 tells gentiles that they are no longer paroikos (non-covenanted germ).
Politeia (Eph 2) as the perfect descriptor for the political connotations of the Hebrew word ezrach (citizen).
Acts 15: Shows that the uncircumcised gentiles were "epistrepho" [converts] and were expected to attend synagogue to learn Torat Moshe (Acts 15:21) on the basis that they had become part of the covenanted people for His name (Am Yisrael) via the conversion of the Holy Spirit (which Peter, in re Cornelius, had symbolized with immersion in a mikveh).
Passover: Familial Symbolism; Federal Institution; Federal Citizenship; Passover Feast as Citizenship Par Excellence
Positive Law Rights: Intimacy Only Found in Positive Commands of Divine Revelation (i.e. Torah); The Correlative Nature of Rights/Duties; The Right to Intimacy; Ruach Immersion as Change of Legal Status
Instruction to Abandon Gentile Identity (1 Cor 12:2; Eph 2; Eph 4, etc)
Spiritual Circumcision as Ritualized Circumcision Par Excellence (Col 2:11-13; Eph 2:11-22; Gal 6:15-16; 1 Cor 7:19; Rom 2:26; Rom 3:29-31
Rights Teachings (Eph 2)
Instruction for Gentiles to Imitate Models of Torah Observance (Phil. 4:9)
Instruction for Gentiles to Follow Mosaic Torah (1 Cor 7:19)
Gentiles as the People Called by His Name (Acts 15)
Gentiles will Receive Persecution for Rejecting Idolatry
Gentiles (along with Jews) are Israel (1 Peter 9-10)
The Gentile Corinthians Celebrated Passover: 1 Cor. 5:7-8
The Colossians Observed Moedim: In Col 2, Paul is attacking the ascetic and gnostic "traditions of men" (2.8) and the "commandments and doctrines of men" (2.22). This is what Paul was attacking: non-Scriptural, man-made traditions. Now observe that kashrut law, Shabbat, New Moon celebrations, these are not "traditions of men" but rather they ARE Scriptural. Thus, Paul was not attacking Scriptural practices. Also, for the acetics to be judging the Torah-observant Colossians for their feasting, the Torah-observant Colossians must've been keeping those feasts.
Gentile Assimilation into Jewish Communities in First Century: Fredriksen, Zetterholm, Nanos, Irshai,
Isaiah 2:2-3; 56:6
Zech 2; 8:22-23