1- I see it more like a meme in the sense that we believe that in the future we will price things in bitcoin. But yes bitcoin price does matter, it must increase over time, otherwise why would people hold it instead of fiat.

2-in btc terms yes your house would probably be worth less over the years yes, you would pay say 1 btc and after a few years it's worth 0.8 btc, good news is all other houses would also be worth less. So in theory if you sold you could afford a similar house. In fiat terms your house would still be worth more.