1. Good to have an easy puzzle this week, as I am only just back from abroad and have to leave again in a couple of days. Nicely constructed too, particularly in that all the three-letter lights around the central square were proper words, even if parts of longer words. Also good to be stimulated to read a rather neglected work by a major poet.
2. The technique of isolating a square within a square has been used before, notably in "Subvert" by Pabulum (no. 3498), in which any word that encroached on the central square had to be entered completely jumbled, and "Lord Dunsany's Problem" by Foxglove (no. 2808), in which the central 8 x 8 in a 14 x 14 (like this one) turned into a chess problem. Others have used the square within a square motif in different ways, some highlighting it in the initial grid (e.g. "Not Quite Tied Test" by Phil Brindall, no. 3216, and "Inner Circle" by Wolfram, no. 3257), others requiring an internal square to be highlighted after solution (e.g. "Friendly Fire" by Leo, no. 3427, and "Tacit Mystery" by Elgin, no. 3484). Room for inventive setting there, especially using different colours (see my comment on last week's).