I am enjoying this take on P&P very much. I am delighted that Richard appears to have found someone, and that Georgiana is dealing so competently with Lord Albert.
A couple of points: in the UK, we do not now (and didn't then) eat biscuits for breakfast. In fact, the UK biscuit and the US one are not the same animal at all. Our biscuits are what you call cookies. Also never, ever cream in tea. Milk yes. Cream no.
And Richard, as an officer in the regular army above the rank of captain, would be allowed the use of his rank as a courtesy after his retirement. He doesn't have to use it, of course, but he could remain Colonel Fitzwilliam.