Seems like a nice group of tables for inspiration. Is there a mistake on the note for the Room Content table? It states "Roll 1d3 times on this table + once on the Atmosphere table" I assume it is supposed to be "roll 1d6 3 times..."
Thank you for the feedback. Regarding your question, it's actually 1d3 because it gives you a range from 1 to 3 Contents + one Atmosphere. To roll 1d3, you use a regular d6: 1-2 = 1; 3-4 = 2; 4-5 = 3.