Is it the wrong group?  ;^D

The mounting bolts for the blades on most mowers gets hard to remove because
of corrosion. Use WD-40 on the threads every time you pull it off to sharpen
it and it should be sharpened whenever you see any tearing of the grass
instead of a clean cut. This will reduce brown spotting.

Personally, I dislike mulching blades as they are a bear to sharpen because
of all the twists and turns that, supposedly, mulches the clippings. If you
decide to buy one, be ready to pay more for sharpening or buy a small angle
grinder and a blade balancing cone so you can do it yourself. Also, your
bagging attachment will not work as well or not at all. . . .no airflow from
the blade.

Back when I was a teen, I just mowed in an inward spiral pattern that threw
the clippings onto uncut grass then the standard blade recut them over and
over. By the time I got to the middle, there was but a handful left to
scatter on the new mown lawn.

The surging could be moisture in the fuel, dust and dirt in air cleaner or
just needing a good tune up. If it's moisture, a tablespoon of HEET will
clear it up. Don't let it go too long or it can damage the carburetor.

Budd