Cowoline, I am fully agree with you. What we need are options, not drastic changes.
So, rethinking my first comment and taking into account your opinion, Halsin should stay polygamous as he is, as a part of wood elf lore, but options must be added for him to become more open to Tav who is monogamous, to make them have a compromise. Plus, his Underdark experience definitely should be either rewised or expanded.
I probably repeat myself and your thoughts too, but I just wanted to make a summary of what I read both in my head and here out loud.