I am really thinking about investing over $15000 of my savings into Bitcoin. Would this be wise? Is BTC safe and stable at this point and this time?
Take it easy. It doesn't mean that the value of price today is high, it will be like that forever. That is a very high risk you are taking, and before anything else, you should read and read more about bitcoin and cryptocurremcy before doing anything else. You'll end up regretting your decisions. It is better now for you to be familiarized in the concept, and deeply think about it, if you ate going to be ready for investing your money on bitcoin.
It all be at risk, even outside crypto investment but above all, we should have to think positive as will and may this risk will give us passive results. However, if we are in doubt for crypto and afraid of its risk, we better not to try. That is why, if we are thinking about this, we should have to plan first and be preferred for any circumstances that might happen to our investment.
Yes, $15k is quite big to start as a newbie and much better not use it all until such time that we are knowledgeable enough in this field.