You are right to have concerns :)
Here are some directed responses:

• Uncapping the ROI is not a good solution. The bot profits then(when I had uncapped ROI) were about 30% of what they are now. I hope this gives you an answer about how much a small uncapped bot makes. The delegators are much better off now. I don't have any solid data to back this up, but I believe @slimwhale is one of the most profitable small bots out there, mainly because of the cap

• I would not care so much about giving high ROI votes, were it not for the fact that @slimwhale runs with leased SP. Let me explain this to you. At the moment, @sliwhale has 1,376 SP in total with 1,357 SP delegated. There are 4 delegators to @slimwhale: myself(316 SP), you with 20SP and two others, with 10 SP each. The rest of the SP, I have leased using minnowbooster and will expire in a few weeks. So I have paid to lease 1000 SP with my own steem, hence each time @slimwhale gave a very high percentage ROI, that steem was literally paid by me.

• Which brings me to my last point, the self voting when the bot is idle(fortunately a rare occurrence). Yes, this is a temporary solution, I am trying to think of something better, like giving votes to delegators, which I am sure would be a very interesting value proposition. The problem is distributing those votes fairly between delegators. As I am currently responsible for delegating more than 95% of the bot SP, yeah, I am self voting, guilty as charged :)