Re: anchor help
the chain serves a few functions. Primarily it adds weight to the anchor, and more important, adds the weight to the end of the anchor to keep it lying flat on the bottom--for the same reason that the longer the scope (line out) the better it holds. Then it also acts as a shock absorber; with any wave action tugging on it from the boat, the chain lifts up and down and not the anchor itself, leaving it buried. Ona rocky/shell bottom it helps protect the line from fraying since it's chain, rather than rope, that's in contact with the bottom.
My experience is that shorter, heavier chain is as good as longer lighter chain. As for the formulas, I do not agree with "chain the length of the boat" as that is overkill.
Like everything with boats, it's all situational. The 7:1 formula is for overnight unattended heavy wind/current conditions; much less will do for typical recreational anchoring, especially in lakes. But straight down does not work. In all cases you need some angle, and a chance for the anchor to dig in. Seldom can you use an anchor like a mooring block.