The answer to the first is easy. Yes, they probably would wear face masks. Washington, Hamilton and Jefferson were all creatures of the Enlightenment, firm believers in science and in progress. Not every Founding Father was like that (John Adams had his doubts about progress), but the three that Presser cites certainly were.
All three were pro-vaxxers, for example. As commanding general of the Continental Army, Washington required in 1777 that all his soldiers be inoculated against smallpox by infecting them with mild cases of the disease, leaving his right-hand man Hamilton to tangle with officers who balked at the edict. Then, after English doctor Edward Jenner introduced vaccination with cowpox, a largely harmless disease that conferred immunity to smallpox, Jefferson enthusiastically embraced the practice as president, conducting trials of the vaccine on his family and neighbors, disseminating it among Native American tribes and promoting the career of the Boston doctor who was Jenner’s chief American disciple. In 1813, Jefferson’s successor and political ally James Madison signed into law a Vaccine Act that made maintaining an adequate supply of smallpox vaccine a federal responsibility and provided free postage for its distribution.
With face masks there is no “proof” in the form of randomized controlled trials that they slow the spread of Covid-19, but there is by now a growing pile of persuasive evidence and a firming scientific consensus that widespread mask-wearing probably helps a lot in keeping the disease under control. It is difficult to imagine Washington, Hamilton or Jefferson observing such a consensus and not putting on a mask in response.