With all due respect, Robbin, you seem to have made two contradictory statements in these last posts. I felt I understood what you had been saying all along, until now.

"The self-interest of marital bliss for me does not automatically erase the generosity of a kindness as does, in my opinion, the vicious self-interest of a cad."

and
"I was not saying the generosity of the promotion was erased."

I don't understand what other "generosity of a kindness" we've been speaking of besides William's promotion.

As to the promotion/proposal combo. It seems he has decided to propose at the first opportunity(ch. 30) before he knows that William's promotion has actually taken place (ch. 31).
ch. 31 Knowing as I do what your feelings as a sister are, I could hardly have borne that any one in the house should share with you in the first knowledge of the news I now bring.
...
Here are the letters which announce it, this moment come to hand.

Now you'll probably tell me that it is convenient acting and lies. , but I forestall you; remember, I have forestalled you ;)