The first may be a Ruby on Rails problem (although I am not sure), possibly exacerbated by the decentralized layout of Mastodon instances. The second seems to be a fundamental design problem.
It seems to me that the original idea of Mastodon was that people would want to participate in communities that focus on specific themes. Many instances are aiming to serve people who are interested in one particular thing. Because of this, finding people and posts on other instances is harder. But reducing my interests to a single dimension is not how I used to use Twitter, so this is a major usability problem for me.
I’m not interested in any kind of community/network/discovery effect. I know which people I want to follow so I just want to find them, be fairly sure it’s really them, and then only read their tweets and retweets.
In other words, just stay on Twitter! Why’d you move to mastodon to begin with?