Is maintaining a superficial relationship with relatives who refuse to adhere to Sharia and who do not offer help when needed considered a severance of kinship ties?

There is no blame upon you for limiting yourself to greeting these people and returning their greetings, and visiting them only on occasions. You will not be considered a severer of kinship by doing so. It is advised to remain steadfast on the principles of truth and not to compromise in matters of religion. Strive for wisdom and gentleness in your interactions, and practice asceticism regarding what is in people's hands so that people may love you. If it is possible to emigrate to another place where you can live without hardship, then do so.