Wikimaker requires a high-bandwidth connection. Anything under 10 Megabits per second download will probably be too slow. Run a speedtest and confirm that your download speed is over 10 Megabits per second (Mbps).
Not currently. We might add more in the future, but not anytime soon.
You don't need to. Once you remove it from any paragraphs you have used it in (using the "x" button, as appropriate), it won't show in your Wiki. It might still appear in the "ready" image list on the right of the screen, but don't worry about that.
Please use the "Contact Us" link above, and describe your question as clearly as possible. If we can answer it, we'll post the answer here and send you the link.