Spoilers, of course.
It’s made even more complicated by the fact that while Scott apparently always intended Dekard to be a Replicant, Harrison Ford strongly disagreed.
It really depends on which version you’re talking about. The director’s cut makes it pretty clear that he is, the original version (which I haven’t seen in years) almost leaves it the other way. There are about 8 other cuts floating around as well, just to confuse the issue. 
It sounds like you’ve got the ‘original’ version. In the directors cut, Deckard has a dream of a unicorn, (Actually a bit of footage from Legend, of all things) and wakes up to find Gaff left him a little origami unicorn. An obvious parallel to the ‘orange body, green legs’ thing with Rachel.
There’s still a few hints in your version, though. All the replicants surround themselves with old photos, so does Deckard. Gaff’s presence, always showing up just AFTER the fighting is done, makes more sense if you take him as the real BR, with Deckard being a weapon that he uses to do the dangerous parts. Like that.
There were also a lot of earlier script versions that basically gave the whole thing away. After ‘You’ve done a man’s job, sir!’ he added ‘But are you really a man?’
The 5/6 thing, though, (the chief tells Deckard that ‘six escaped, but one was fried passing through a barrier,’ but there are only four reps, Roy, Leon, Priss, and Zhora) whatever Scott says now, wasn’t supposed to be a clue. There were six replicants in one version of the script, (there were a LOT) but the ‘nanny’ rep got cut out
Some people think that this kills the ‘man learning the value of life’ message, but I disagree. It really doesn’t MATTER if Deckard is a replicant or not. They’re just as alive, and just as aware, as humans are.
You might want to check out the Blade Runner Movie Faq, at BLADE RUNNER Frequently Asked Questions (FAQ)
Now, the real question is whether or not Silia is a Boomer.
Is is POSSIBLE to spoil Citizen Kane? It’s been prespoiled by about a million sitcoms and pundits.