The colonel's behaviour is that of an admirer, I agree, and Darcy couldn't help but be aware of it. I know he makes mistakes about people's feelings (and the lack thereof) but two men attracted to the same woman, who is charming and prone to laying down the gaunlet, must be aware of the competition. There is wonderful sexual tension at the piano. I 'read' an unspoken challenge there - Col saying "I might not be able to marry her but I'm the one she likes!" Not that I think he is a nasty person - just human. Darcy calls all the shots, but the colonel has the odd string to his bow. (Sorry - I know it's not very funny but I couldn't stop myself.)

I doubt that the colonel knew Darcy would propose, though.:-) I can't see Darcy telling him, even if they are good friends, and it would not be what anyone expects. However, if he feels he will need assistance from Darcy after he's married, he might back down.(I keep seeing stags, quivers, snortings - so uncivilised!)

We don't know the colonel's exact financial situation - some have suggested he is in his father's own volunteer regiment and therefore completely dependent on his father for money. I think he may just have expensive habits and relies on his wealthy relatives to supply some of them. I think he earns enough to support a wife in modest respectablity because Elizabeth seems to see him as a potential husband. She's not in love with him, but would possibly have married him if he asked.