BluelsYou, you can definitely have gas/air. Be prepared to go in knowing 'when' you want it. My first HB my midwife didn't want me to have it during the pushing part. I pushed for just under 5 hours. I was in a pool for most of it (though i got out in the end, and he was born with me kneeling on one knee). My 2nd HB, the midwife couldn't understand why the first one they'd said no.
Your husband is worried about 'instant' medical care... let him know that if you are in hospital, they can't just whisk you immediately into theatre, they need to prep the room, get the docs, etc. They can do all of that while you are in the ambulance on the way to the hospital, so assuming you're not an hour away, you tend to get the same response for emergency c sections, etc. There will be a box of 'kit' left at your house near the time of the birth, which includes various drugs that might be needed at the time.
You are also far less likely to get an 'unnecessary' intervention. For example, my 5 hour 'push'. If i'd been in hospital, it would have been an 'emergency' c-s after 2 hours, which is the box they need to tick when you're on their turf. As it was, baby was happy, just not ready to come out yet (turned out i had a cervical lip and he was bungy-ing). I kept going at home and was much happier and recovered much faster than if he'd been c/s. I actually had 3 midwives (one for the baby, one for the mother, and by coincidence, a student midwife) at each of my home births, for the entire time. When i gave birth in hospital, which was awful, i had one pop her head in occasionally because there were not enough to go around. She was in charge; ushered me into the room, then said she'd go get 'my' midwife, and literally had no-one to bring back so just stopped by when she could. my husband had to go find someone when things were coming to a head (so to speak). one of the midwives will hang around for about 2 hours after the birth (and until you've met certain criteria, such as being able to pee!), to make sure all is ok.
My DP was also worried about my medical care - particularly since on the 2nd HB, i had developed a history of major hemorrhage from a miscarriage, and i had to show him all the stats, etc, but he realised that actually it's better at home (unless you're high risk, like i was for various reasons in my last birth).