Regarding 2) A special panel to select both planet and asteroid at the same time wold be ideal, but if this entails too much development time, then just displaying one asteroid on the side and having three planets to pick from probably makes the most narrative sense.
Regarding 4) "Cross-Disciplinary Research" - "Completing any Technology allows Science points to be spent in the closest Technologies directly above and below in the same column". So, the player can choose between jumping the branches on the technology tree OR whatever the other Wellness Bonus is (like reducing the cost of Tier 2 buildings, if I remember correctly).