Hello, Tribal_games.
Based on those three point you have given, I would like to share the response for that (Disclaimer: I am not developer or contributor, I am just a player)
On point one, I think you can make a feature request about "Don't pause when opening certain menu" in Mindustry suggestion in GitHub. (Require you a GitHub account)
Second, the resource gathering can be done through direct mining, drills, and using logics to units that has ability to mine.
Last but not least point, the time acceleration feature has been proposed many times even since long time ago and Anuke (Developer) decided not to implement this feature based in Mindustry GitHub.
If you would like to get involved, you can check Mindustry GitHub which is linked on the description. At there you can contribute, suggest, report bugs, etc. there.
Thanks.