I didn't really take to Greg Sutton - I think because his first interactions with Petra come across as really patronising and that rubbed me up the wrong way though I suspect to 1970s eyes they would have seemed amusing (and maybe faintly charming, I don't know - I mean I wasn't born until about 6 months after this aired so I've no idea how his behaviour looked to contemporary eyes) and after that I felt like he was mostly just there telling people it was all terrible but not actually doing much.

I don't think the green ooze has been mentioned again on the show - but I bet its been explained in spinoffery somewhere.