I see a few possibillities. 71B at those temperatures is a very good yeast. The Staggered Feeding is also good for keeping yeast happy, but you are missing buffering the ph of your must. Next 5 gallon batch, add 3/4 Tablespoon of potassium bicarbonate (aka K2CO3 or potassium carbonate). This will add potassium, which is a limiting nutrient in honey, and Will also prevent the ph from dropping too low. Low ph will cause the yeast to be unhappy and make chemical flavors and will stall fermentation if it drops below a ph of 3.
Another possible source of chemical flavor is your fruit or honey. Any pesticide in your fruit or in the honey will show up in the mead. I had a batch of honey that I gave up on due to the bees pollinating a pesticide treated field! Try organic fruit or removing the peel and a different honey source. The Bee Folks are a reliable source as well as Northern Brewer.
If the chemical flavor is not pesticide, it will age out over time. A clean ferment supported by SNA and ph buffering will always produce less off flavors and require less aging.
By the way, oxidation tastes like wet cardboard. Oxidation is a non issue in mead. I've had bungs pop off for over a month with no oxidation flavor at all. It's a problem in beer due to a chemical reaction with hops.
Sediment is normal in the bottle, but can be minimized by allowing the mead to clear completely before bottling. I mean crystal clear that you can read a newspaper through it. I have taking to using superkleer as of late, but it may strip some flavor from the mead. Your choice!
For more mead specific information, check out gotmead.com. Hope that helps!