Can microwave emitters serve as a makeshift home defence weapon?

Although many of us have MW ovens, I can name like one Saw movie and one DIY channel that showed it's potential to melt things, and I watch\read a lot of gore and torture on the web. It won't be used in a military context due to how power consumption and short distance make it useless. But in a Home Alone situation it seems promising, especially as a trap because you won't stop anyone with that immidiately.

My qustions are:

1. How a breaf exposure is dangerous, and can it be used not to harm but to scare off?
2. How it'd be treated legally due to it's weirdness?
3. What are general downsides of that, like reflecting it back to the sender or dealing irreversible fatal damage etc?

I'm stupid at basic physics so I'm sure I miss something.