A baronet is not a peer. The title is a hereditary honour descending from father to son. Thus Thomas Wharton was given the honour by Henry VIII and thereafter stuck Sir in front of his name and Bt after it, If he had no son, the title would become extinct. If a later holder of the title sires no son, the title descends to the nearest male descendant of a former holder.
A baronet's wife takes the title Lady with her surname, thus Lady Wharton. She is not entitles to be called The Lady Wharton. The is not generally used now, but was once in general use - historical authors take note!
A baronet is addressed by his title and forename ie Sir Thomas. In writing you would address him as Sir, and his wife as Madam. The envelope would be formally addressed to Sir Thomas Wharton,bt and for his wife: Lady Wharton.
Widows retain the style until the succeeding baronet marries. The new wife takes the title and the widow adopts The Dowager Lady Wharton. If she marries again, she takes the same status as her new husband. In other words, if she marries a commoner, then she becomes Mrs Jane Harris or whatever. Until re-marriage they are addressed by forename and title. Children of baronets have no titles. They are plain Mr and Miss.
Went up the hill for a walk today and almost blew away. Beautiful and bright, but the wind! Tears ran down my cheeks!