It seems like people are currently in this rush of making as much money as possible for themselves but I think in general there is a negative stigma around it.
Despite the fact I see people self-upvote I don't think I would want it outlawed as people should be entitled to be able to get some sort of ROI from their money and as exyle said how users don't get angry with those who make money with facebook or twitter and I think it may take away a stimulus for people to buy SP.
Your voting power will reduce about 1.5% with the each next voting at 100% of upvote strength. regardless is it selfupvote, or not. So it means you will have chance to upvote yourself or someone else just 10 times, and then you will have to wait about a day to recover your voting power to 100%
Linear. It depends on persentage of upvoting (100% by default) So the each next upvote will cost less than previous. you can visit steemnow.com it is good service to check your current voting power. There is calculator that will show cost of upvote at different conditions.
Well, I looked at your stats, you will have to wait 4-5 days to recover to 100% of voting power. No voting suggested in this period. The price of upvote depends on Steem Power, not reputation. You have rewards for your activity on the site partly in steem power (SP), partly in steem dollars (SBD). You can convert earned steem dollars into Steem (token) and then convert it into fiat carrency, keep as cryptocurrency or by a SteemPower. The last is called power-up. As more steempower you have as bigger your upvote sum. You can buy Steem for your money and then convert it in Steem Power - to become investor, but remember the back operation is not so easy - converting SteemPower into Steem (powerdown) takes a lot of time.