But, what really got to me was the fact that from studying these boards, I was under the impression that I could trade in some counter service credits for a table service credit.
I was told, at check in, that certain restaurants will trade in Two CS's for one TS. I guess Sci-Fi was just not doing it.
I'm a little confused

When you checked in, did you ask the CM if you could do that, or did the CM just volunteer that incorrect info? You said from studying these boards that was the impression you were under. The only thing I've seen on these boards on that topic was people asking, "Can we trade 2 CS for 1 TS?" or "Wouldn't it be nice if we could?" and the answer is always, "Yes, it would be nice, but
no, it does not work that way."
A couple of people have reported that they had a CS or two left on their last day, and accommodating CM's at a gift shop or food court might have let them trade one CS for a couple of snacks, but that is not a rule written anywhere in the
DDP literature and seems to be the exception rather than the norm. And as bicker has pointed out numerous times to me,

the bargain pricing of the DDP also factors in a certain amount of non-use -- ie: Disney is counting on that overall a certain percentage of those CS and snack credits are going to be left over and are not refundable and can't be used on a later visit. But I've carefully planned our itinerary and don't intend for ANY credits to be left over
The average values for a CS meal range from $10-$13 per person. A buffet ranges from $24-$34 per person. A standard TS meal averages about $22-$41 per person but can be much, much more. So it really wouldn't make financial sense for Disney to allow 2 CS to be traded for 1 TS, especially since the DDP is already a significant discount for the guests.