They lived beyond their income, but still it was nothing in comparison of Enscombe; she did not cease to love her husband, but she wanted at once to be the wife of Captain Weston, and Miss Churchill of Enscombe. (Chapter 2)

I tried to look up Enscombe on-line and came upon Encomber instead which sounded right to my ears as the root for Enscombe. Hopefully I am not dreadfully wrong! Unreasonable regret at the anger of her brother, the master of Enscombe and at the loss of the luxuries of Enscombe herself hampers the former Miss Churchill’s ability to enjoy her situation in life and turns what should have been a happy marriage into an unhappy one. In this way Enscombe is an encumbrance and I think so earns its name:

Encomber: \En*com"ber\, v. t. See Encumber. [Obs.] (Ref: Webster’s Revised Unabridged Dictionary © 1996, 1998 MICRA, Inc.)

Encumber: To clog; to load; to impede; to entangle; to embarrass; to load with debts. (Ref: A Dictionary of the English Language by Samuel Johnson, John Walker, Robert S. Jameson, 1828.)

Encumber: Origin: 1300–50; ME encombren…see source. (Ref: Dictionary.com Unabridged (v 1.1), Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006)

Fortunately for him, Highbury, including Randalls in the same parish, and Donwell Abbey in the parish adjoining, the seat of Mr. Knightley, comprehended many such. (Chapter 3)

I agree with your view that Mr. Knightley’s life is a bit monastically in tune with living in an abbey. Add Don (a title of honor) and well we have an honored person who is right and quite unmarried. I would also like to say so far Mr. Knightley seems to me well worth to putting on or investing in:

Don: A title of honour in Spain.

To Don: To put on; to invest with.

Well: No ill; not unhappily; not wickedly; skillfully; properly; in a laudable manner; not amiss; not unsuccessfully; not erroneously; not insufficiently; not defectively; to a degree that gives pleasure; with praise; favourably. Well is sometimes like the French bien; a term on concession. Conveniently; suitably. It is a word by which something is admitted as the ground for a conclusion, as well, let’s away. As well as, Together with; not less than. Well nigh, Nearly; almost. Well enough, In a moderate degree; tolerably. It is used much in composition to express anything right, laudable, or not defective, as well-affected; well-aimed; well-appointed, etc.

(Ref: A Dictionary of the English Language by Samuel Johnson, John Walker, Robert S. Jameson, 1828.)