Once you click the bed once, it will automatically start/stop waves. After 15 seconds of completing a wave, the next wave starts. Idk about the ammo consumption, but from my playthroughs that seemed to work fine. The seed sheds spawn seeds if you have unlocked the specific seed type. There were a lot of automatic mechanics designed to help the player, so the refilling could be because of that.
On the other hand, I'm so happy this game stabilized a decent amount for launch. If you saw this game even 24 hours ago, it felt like a whole different game. Maybe a few bugs did slip through, but regardless thank you for playing!