So, I used a bit over 4 lbs of honey per gallon and ended up with an OG of 1.135. I pitched my yeast, had a very healthy fermentation, and after about 2 months I racked it into secondary and the gravity was down to 1.040....
Racking it before you were near the final gravity that you were looking for is where your ferment slowed down.
Since then, 7 months have passed (making this mead about 9 months old) and I've racked it twice but the gravity is not going down....
The more times you rack the less chance any further fermentation will occur as you are slowly seperating mead from any yeast that may still be kicking.
Furthermore, although it cleared a bit, it is still pretty hazy. Although I like sweeter meads, this mead is pretty damn sweet. How do I know if I should pitch more yeast? Would it even be a good idea? I'd like to do something because it was an expensive project that I wouldn't like to have be a failure. Any help that y'all can provide would be MOST appreciated...
Definitely does not have to go into the fail column, you have a few options.
1) you can dilute, you've made other batches of mead, what type were they and were they dry or at least dryer? if they were a traditional or at least complimentary flavors and dryer than this batch you can blend them, cutting the sweetness of this one....there is the water or wine dilution method but one dilutes flavors and abv the other ehhh, not a fan of the idea.
2) you can give it some nutrients and pitch some yeast, but your options are kind of limited for yeast strains because of the alcohol level you already have so something like 1118 is what you will need to use just remember that you are only sitting on a gravity of 1.04, so if the yeast gets started it will burn through every bit of sugar you have left and take it super dry. Not ruining your batch, just adding steps later of backsweetening to bring sweetness back if that is your desired finish. kind of like chasing your goal back and forth.
3) Even with a mead that alone is sweeter than you like there is the option of not trying to get rid of the sweet but balancing it out so it's not cloying. Look into acid blends and tannins or aging on oak chips, the first two you can add in small amounts until the balance reaches a point where it is pleasant to you and not overpowering and leaving you chasing it back again. Mead doesn't have to be fermented dry to not be annoyingly sweet.
4) Well I'm sure I overlooked something another poster will thow out there as an idea for you. Just take a moment and contemplate each suggestion before leaping at any, not so much what will immediately occur in your carboy, but what will happen next, kind of like playing chess, think a couple steps ahead and see what options will get you to the end product you desire with the least number of moves.
For the haze still in it, there are the options of time (not always 100% effective) fining agents (i've read K&C works well) after you get it to where you are happy with the flavor you could try cold crashing it, see if anything more falls out.
All is definitely not lost, it sounds like you have a delicious project going, just have to decide on what types of small tweaks to make (yes at this stage a bunch of small adjustments will be more advantageous than a huge leap somewhere) and you'll be enjoying an awesome glass of mead in the future.