1) That is true! Rooms with a lot of enemies are dangerous.
2) Yes, it's far from ideal.
Explanation: There is one grass tile type that is covering line of sight (to your right in the image, that looks like a corn plant). It is true that it's a bit of a gamble. In this case you can safely move up because plants will never spawn in the a doorway. Also, by definition plants can't spawn adjacent to each other. It doesn't solve all situations but it helps sometimes.
I hear you. I might redo that tile to indicate the blockage better. This system is on the list to iterate on in a sequel.
3) If it's any help, killing a scorpion with any ability will avoid blindness. You have to evaluate if it's worth it.