1)
How thick was the lid of the Aron?
1
Which the Gemara in Sukah, 5a learns from the smallest of the Keilim - the Misgeres (the frame around the Shulchan), which was a Tefach wide, as the Torah specifically states. See Torah Temimah, mnote 21.
2
Refer also to 25:11:2:1*.
2)
Why was the Kapores made specifically of gold?