It is a mess and I dont' quite have an understanding of it yet. Likely we have a whole mix up of things Tolkien wrote at different times. Don't know if resolution is possible, but I hope to figure it out.
About the Elves marrying and having kids, that's from Quenti and Eldar, and as MM concluded, that 50 years has to be Years of the Sun because of the comparison with growth rate of men/children. Here's something really wierd though, none of the dates of marriage/having kids for the elves fit into that. It's way off, like 500 years instead of 50, but if you used 144 instead of 9.58, it's even futher off. I really dont' know what to think. For now I stick with 9.58 though, don't see any problems with it yet and can find no reason why 144 is better.
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