He was truthful since he waited for F to die. He might not have heard immediately, hence the extra years.
As a medic, if he had committed bigamy and been found out, the consequences and scandal would probably have been very damaging. Once F was dead, he truly was a widower.
There's all sorts of reasons why he might have given up surgery as he got older. Maybe wasn't strong enough anymore, or his hands were no longer steady. Maybe he grew tired of it - no anesthetics, no understanding of post-operation infections (all of that came later in the century). Also, big changes were happening in the second half of the 19th century (with the predictable resistance), maybe he felt that he couldn't, or didn't want to change.

If an opportunity to do something else came up, I think that I would have taken it!

The following text is a quote from the RCS webpage (the rest of which is mostly about modern surgeons):

"In most other parts of the world all medical practitioners, physicians and surgeons alike, are referred to as Dr while in the UK surgeons are usually referred to as Mr/Miss/Ms/Mrs. This is because, from the Middle Ages physicians had to embark on formal university training to gain possession of a degree in medicine before they could enter practice. The possession of this degree, a doctorate, entitled them to the title of ‘Doctor of Medicine’ or Doctor.

The training of surgeons until the mid-19th century was different. They did not have to go to university to gain a degree; instead they usually served as an apprentice to a surgeon. Afterwards they took an examination. In London, after 1745, this was conducted by the Surgeons' Company and after 1800 by The Royal College of Surgeons. If successful they were awarded a diploma, not a degree, therefore they were unable to call themselves 'Doctor', and stayed instead with the title 'Mr'.

Outside London and in the largest cities, the surgeon served as an apprentice like many other tradesmen, but did not necessarily take any examination."