For anyone interested in Blade Runner and its (painful) creation, I heartily recommend the engrossing documentary Dangerous Days that can be found on the Final Cut release. It will answer most, if not all of your questions, gentlemen.
In any case, the original theatrical version has no major hints of Deckard being a replicant - unicorn scene is cut & the hastily added voiceover (though the first draft of the screenplay actually utilised a - different - VO) explains only that Rachael doesn't have a limited life span, hence the "happy ending" (enhanced by the countryside scenery). The subtlety is still there (e.g. photographs in Deckard's apartment) but the producers moved the story away from Scott's intentions.
If we go by the book, though, then Deckard is human.