These might not be 100% accurate since I can't check the details right now, but it should give you the right idea.
- Ichor should start spawning right at the start of the game
- It spawn only in caves
- There should be about 4 different maps it spawns at
- It always spawns at preset location, one per map
- Spawn is chosen randomly
- Ichor respawns one month after you pick it up
- Once one ichor container is spawned, no new container will spawn untill you pick the old one up and wait one month for new one to spawn
As for the ghouls:
- They are not tied to Ichor spawning in any way
- They spawn on a timer that starts the moment you enter any cave map
- Each map spawns a ghoul at different time value. Ghouls take longer to spawn in maps that are near the surface, while deeper caves spawn them sooner
- This timer is reset by skipping a week in any way. Just entering and leaving a cave will not reset it
Hope this helps.