Re: How does Signal fund itself?
Not quite. Signal was originally and is developed by Moxie Marlinspike and others, and then at a later point in time WhatsApp liked what Signal were doing regarding encryption and so they also adopted Signal's encryption technology in WhatsApp.
Even later, after WhatsApp sold itself to Facebook, and after he didn't like the direction that Facebook was going in, Brian Acton, one of the WhatsApp founders, decided to more strongly support Signal and helped to set up and finance the Signal Technology Foundation (using some of the money he earned from the sale of WhatsApp to Facebook), which supports the ongoing development of Signal.
[Interestingly, the support for the Signal Technology Foundation is apparently in the form of an interest-free loan (see page 31 of non-textual PDF), rather than a donation (thanks to Signal Technology Foundation article on Wikipedia for the link).]