I'm new in town, and it's a delight to follow your discussions!
On free will: I'm inclined to doubt that free will as usually conceived is a coherent idea. On the one hand, 'freedom', as a property pertaining to alterations of mental states, connotes a mysterious suspension of causal influence from the rest of the world. On the other hand, however, few would accept an analysis in terms of _randomly_ engendered alterations. It is perhaps more instructive to understand free will in terms of downwards causation. Mental states are higher-level features of certain machines such as brains, by (very rough) analogy with liquidity being a higher-lever feature of H2O molecules in motion. Some of these states have in turn a causal impact on constitutive elements on the lower level (e.g. neuronal firing patterns). This dwe might think of as "free will". On this analysis, the distinction between the 1. and 3. person perspectives is purely epistemic: The panscient spectator would have no use for it. But I fail to see any special connection between free will, however understood, and the multiversum models - pace e.g. Deutsch in "Fabric of Reality". Maybe a multiversum view is required for a coherent analysis of counterfactuals, hence of causality, and hence of downwards causation; but that's a much more general matter. Best, -- Gisle Tangenes