Is there anyway to maybe demand Electrum to pay me the money due the their failure to secure my funds?
That would be a bit like demanding money from the maker of a piggybank because a burglar broke into your house, smashed your piggybank and ran away with your money.
So I haven't used my electrum account in a while, but I had about .5 btc on it. I opened it today just to find out all my btc was sent somewhere as payment. I sure as hell did nod send it, and nobody who uses my pc or phone has the knowledge of how to use it, i.e mom and 12 yo brother.
Are you reasonably sure that neither your mom nor your 12 yo brother have been unknowingly downloading malware or visiting malware websites?
Using crypto on a "general use" and/or shared computer is not really recommended from a security standpoint. It's very difficult to know exactly what other people have been up to on that computer, and it's possible something they have done has compromised it, even if you have been super careful.
How can I check my device's security?
Possibly start with some scanners like "Spybot" or "Malwarebytes"... Try having a look at the "Bleeping Computer" forums for assistance:
https://www.bleepingcomputer.com/forums/f/22/virus-trojan-spyware-and-malware-removal-help/Is there a way to cancel a transaction or something?
No. Once it is completed, it is completely irreversible.
Do you know anyone who might be able to retrieve my funds?
The only person who can return your funds to you... are the person(s) that currently have them... which I would suggest they are very unlikely to do.
