Welcome! I hope that you find comfort here (even if it's just people to listen to you at the moment). I don't think you'll find any judgement here about allegedly hot housing your child on this forum, because most of us know what that feels like and know that it simply isn't true.
Much of what you describe sounds a lot like my DS at that age, particularly with respect to the signing and the large attention span. We signed with him starting around 6 months and didn't get any signs back for awhile, but then around 14 months he started signing like crazy. And when he did, they were never about needs (hungry, wet, more); they were about interests (book, bird, dog). His first attempt at humor was through signing.
I had had to fend off concerns from my uninformed relatives that signing would delay his speech. Nothing could have been further from the truth! Only a few months after he started signing, he started talking as if he had been an early talker (and dropped the signs, oddly enough... which was kind of frustrating because he didn't quite have the diction down to understand what he was saying for another few months). By 22 months, he was recounting stories and speaking in fully-formed paragraphs.
We were in a position like you where we noticed that he seemed rather advanced compared to most other kids his age (the precocious speech was what tipped us off), but it wasn't particularly important. At this point, I wouldn't worry about whether your daughter is bright, gifted, or what any of that means (it doesn't sound like you were, anyways). Since you get to spend so much time with her, the best thing you can do is follow her interests and see where it leads the both of you.
When we finally had his intelligence assessed with the WISC last year for educational purposes (he was 6.5), we were shocked to learn that he was not just bright but also highly gifted (i.e., exceptional even within the gifted population). So you never really know what the future is going to bring... but it's a fun ride filled with all kinds of unexpected turns!
