You need to go into the hospital, and your DH needs to be a man and come home.
I know it's expensive (I wish I could just fly you all to Canada, it makes me sick to think you need to think about money when it comes to your health) -- but you need medical care. Dehydration this severe in second trimester is nothing to fool around with. We have lost babies here due to severe, unproperly treated HG in the second trimester. We have had forum members go into kidney failure and end up in the ICU. We even had one member die in 2005.
Please, I am begging you, for your safety and the safety of your baby, go to the hospital. Bring your son if you have to. Just go. I have been at HER since 2006 (six years) and the scenario you're describing, where you need to go into the ER but don't for one serious reason or another, rarely turns out well. It often leads to long, long hospital stays or worse.
I am not trying to unduly frighten you -- I am trying to impress upon you the potential seriousness of your situation. I care about you. I am worried about you. I want to smack your husband until he sees stars.
Where are you in the U.S.? Perhaps one of our senior forum members lives there (someone not HGing) and could help. We love to help our HG sisters here!
Many hugs. Keep posting. We're here to help.