What yeast did you use??
Irish moss has NO place in mead. For one thing, you shouldn't be heating the mead. For another, as far as I know, there's no proteins that need help breaking. I also would NOT add ANY acid to mead unless it was determined you NEEDED it via a PH test.
Another thing 6# of honey in a 3 gallon batch is a low OG mead. Your OG should have been about 1.069 +/-. IF you had selected wine yeast, it would have finished dry.
Let me guess, you got the recipe from the Joy of Home Brewing book... Do yourself a favor (next time), don't use those recipes. At least not without bouncing the recipe through others that have made mead, either here or on the Got Mead? web site/forums. With as expensive GOOD quality honey can be, using those recipes could be a serious waste of funds.
How long did you let it go in primary? I typically go a least two, if not three months in primary for my meads. I then rack at least a few times, at least a few months apart, to help get it to really clear up. Right now, I have two batches, destined to be about 14% that have been going since 12/4. With the yeast I used, you actually want to rack them sooner than other yeast I've used. But, until fermentation is finished, I'm not touching them. I expect to rack no sooner than about a month from when they were started.
One of the batches I started last year, went a full year in bulk form. I aged it on oak cubes for about 5-6 weeks, before racking to a keg, to cold crash it. I then bottled from the keg (no CO2 pressure was used in the keg, just purged the atmosphere from the keg and then left a blanket of CO2 on the mead). It's the clearest batch I've bottled so far. So clear that I intend to use the same process for all future mead batches. I stabilized (with chemicals) two other batches, and I'm not nearly as happy with those as this batch.
IF you formulated the recipe to a reasonable level, you would get it to ferment fully, with the yeast selected (Lalvin wine yeast being my primary choice), then rack to get off the lee's before you even think about adding oak and such. Any mead under 12%, I would assume needs a solid 6 months to get good. 12-16%, figure 6-9 months (maybe longer). 17-18%, a full year. 18-21%, 15-18 months. Over 21% and count on 18-24 months before it's ready for drinking.
If you didn't ferment at least to the limit of the yeast you used, then you'll need to either stabilize the mead, or make sure you get all the yeast out of it BEFORE you attempt to back sweeten it. OR, you can slowly add some honey to it, letting it ferment as it can, until you get it close to a sweetness level you like. Just leave it at least a bit more dry than you think you want. As it ages, chances are it will get to where you actually want it to be. Otherwise, it will become too sweet for you.
Mead tends to get sweeter as you age it, post fermentation. This is why many people don't back sweeten their mead until it's almost ready for bottles. It's also why many of us choose to age in bulk form until the last possible moment, before bottling. While still in a single batch/bulk form, you can tinker with it. Once it's in bottles, you're pretty much done tweaking it.
I would highly recommend leaving it in bulk form for as long as possible. If you're not patient (at all) and really want to force things, you could stabilize the mead, then cold crash it, before back-sweetening. But if you don't let it age to a decent level first, you could be make it far too sweet later. If it's DRY, then time, will help to soften it. If it's tart due to the acid you added, then you could have more issues. But, time could resolve that. Just leave it in bulk form.