Amber needs saving, Help!

So I brewed an amber using Palmers big basin ale(red nectar clone) recipe. I came up short on the OG. should have been 1.055 per Palmer. I got 1.049. not crazy off but it only droped to 1.018 I was expecting lower. I only pitched a smack pack of northwest ale per a “experienced brewers recommendation” and fermented in my magic closet at 66-68. I just transferred the bulk of it to a keg last night and saved a gallon or so for bottling and then tasted what was left in the tubes. Not impressed. I put CO2 to it and shoved it in the fridge hoping for the best but it will probably not work out. Its to bitter and is lacking malt character to back it up. At least it looks good lol. Im thinking of making a gallon of concentrated hopless wort and reseting this one. the question is should I just add back the keg contents to the original carboy (6.5) and stir up the yeast/trub a bit  or should start fresh in another vessel and pitch a fresh starter/monster starter? also, I know better than to aerate the fermented brew so would aerteing the starter and new wort be enough?  Here is the recipie from Brew Target.

Black Hat Amber 1 - American Amber Ale

Batch Size: 5.670 gal
Boil Size: 3.670 gal
Boil Time: 60.000 min
Efficiency: 70%
OG: 1.048
FG: 1.015
ABV: 4.3%
Bitterness: 40.8 IBUs (Tinseth)
Color: 17 SRM (Morey)

Fermentables

Name    Type  Amount Mashed Late Yield Color
Liquid Extract (LME) - Pale Extract 3.300 lb    No  No  78%  8 L
Liquid Extract (LME) - Pale Extract 3.300 lb    No  Yes  78%  8 L
  Caramel/Crystal Malt - 60L  Grain 3.000 lb    Yes  No  74%  60 L
Total grain: 9.600 lb

Hops

Name Alpha  Amount  Use      Time  Form  IBU
Centennial 10.0% 0.500 oz Boil 60.000 min Pellet 16.9
Mount Hood  7.0% 1.000 oz Boil 30.000 min  Leaf 16.4
Willamette  5.0% 1.000 oz Boil 15.000 min  Leaf  7.6

Yeast

Name Type  Form    Amount  Stage
Wyeast - Northwest Ale  Ale Liquid 0.528 cup Primary

I wouldn’t do any additions at this point - it likely won’t improve the beer more than just letting it mellow over time.  Given that your concern is bitterness, you really can’t fix that very well at this stage of the game IMHO.  Just give it more time.  You can always bottle it and taste it every couple weeks.  At 40 IBU’s it shouldn’t seem too bitter, but your palate may say otherwise…

+1.  I wouldn’t think a 40 IBU beer that finished @ 1.018 would seem that bitter, but hop bitterness isn’t for everyone’s tastes. But I would leave it alone. Bitterness diminishes over time - it won’t seem as bitter in a couple weeks, less yet as time goes by. Very worst case, you could brew another underhopped amber and blend until you get your desired result. I say leave it as is - it’ll get there.

it’s also really misleading to judge the bitterness of a beer from samples tasted while packaging. Yeast have a tendency to collect alpha acids and can taste very very sharply bitter. After the yeast drop you will likely enjoy the beer a lot more. it’s hard to taste anything else when you’re sucking down a mouthful of bitter yeast corpses.

Agreed with above.  Let the beer mellow for 3-4 wks and you will be singing a different tune.  The hops will mellow out and meld with the malt.  As for your 1.018 FG, different maltsters that produce LME will have different fermentabilities.  If you desire a lower FG, you could either swap out a bit of the malt extract for simple cane sugar or try switching to DME which typically will dry out more than LME (at least IME).

Ok. aging it is.
I have several gallons in a keg that will be drinkable this weekend. Hopefully the carbing/cold crash will yeild a slightly better brew and I can rest easy. thanks for the help. I will report back.

Does this qualify as an Amber Alert?

So I poured a glass last night and it is bordering on pretty good. Its under carbed and still a little bitter for style/what I was hoping for but I dig it. Gonna crank up the CO2 and wait another week . Patience pays off again. Thanks to all for the advice to wait it out.