1. We don't know if the tomb actually contains his remains.
2. The Alliance was never in a position to build the tomb. Arthas rolled and and wiped the city out, then the Scourge and Dreadlords controlled the remains and renovated the Undercity.
1. It doesn't contain his remains. Terenas' remains were scattered at Andorhal by Arthas.
2. Yes they were. Not only were they in a position to retrieve the remains in the first place but we see in TFT that the Alliance retained a presence in Capital City all through RoC, thanks to the presence of the Silver Hand.
They keep the candles lit and apparently replace them regularly.
Yeah, candles are great for lighting a room that isn't completely lit by the wall torches already there.
That's idiotic. And very, very clearly not what was being conveyed in the quote.
As Arkturas pointed out, simple english disagrees with you.