I suppose 'Les enfants de la flamme'.
Normally, no. You can have loyalty to several clans or tribe, but you belong only to 1.
No, especially if you keep a loyalty passion to the Ernaldori. If asked, you just answer this is your birth clan but you now belong to another. If just for marriage, changing clan is common.
Nothing in the tribes forbids a territorial discontinuity. This is a matter of loyalty, not of contiguous territories. Corsica is not contiguous with metropolitan France, but is a part of it (and Algeria was), and left arm islands are not contiguous with the holy country but part of it, usw. On the contrary, Upland marsh is inside the kingdom of Sartar, but not part of it, like Vatican or San Marino for Italy.