1. I don't think you can sell artifacts, so it's a moot point ;-) Might as well use it since it will give dwarfs good thoughts to do so.
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4. There is no way that I know of to ensure that bags are never used for picking up seeds. What I do is make a stockpile for cloth bags (with no bins) and have it give to the glass furnace. If you want to reserve 10 bags, then make the stockpile 10 tiles in size. Usually I make these bags out of a specific cloth, or dyed with a specific dye, but you don't have to. Then I have a manager job at my clothier's to make 1 bag every time I have less than 10 bags (and if I've picked pigtail cloth for sand bags, then I can make it based on pigtail cloth bags -- you get the idea). I have that job repeating every day. Then every time a dwarf nicks a sandbag to do something else, a dwarf makes a new pigtail bag and delivers it to the furnace stockpile stockpile.
It's a shame that you can't stop dwarfs from using whatever bag for collecting seeds, but you can use stockpile links to control every other bag usage. I admit that this kind of logical puzzle is half the fun of the game for me and while it is tedious to set up, it's not micro managing per se. (And before PatrikLundell mentions it, yes, you *do* have to actively manage growing/shearing of the cloth materials, which sucks ;-) ). BTW, never use bins for things that are connected to manager conditions otherwise everytime a dwarf picks up a bin you end up making more of that thing :-P