Smithing Furnishing Skills

Hi, I have a question about the amount of skill the furnishings give.

BG says the Hearth, Anvil and Sign give +1, is this plus one each or only gives +1 total for the moghancement?

It also says the stall give +5, Is this because of the mega moghancement (which come if combined with other furnishings, I know)?

What the max +skill you can get from furnishings?

Thank You