Firstly apols if I repeat what's already been said - I'm afraid I don't have time to read all the threads.
I'll deal with your husband's concerns first.
He is plainly wrong about the tight fanjo thing. He's never had a baby, so he's taken one example out of the billions of births that have happened on this planet and has extrapolated the most absurd 'rule' about birth that I've ever heard.
Basically he doesn't know what he's talking about. I had a 3rd degree tear, was sewn up a bit small (only on the outside lip - sorry for detail!) and am about to have a minor op to fix that. However, my fanjo has never been tighter. Even if you are one of the extremely unlucky 5% or so who have 3rd, let alone 4th degree tears, so long as you keep up pelvic floor lifts you'll be fine with regard to tightness. A little leakage may possibly occur occasionally but only if you don't do the lifts every week or so.
Lots of women on this site have said their fanjos were tighter than ever after having a baby, because giving birth forces you to get to know your body better than ever and gives you a determination to fix whatever's out of joint.
If you have a elective caesarean he had better be prepared take 6-8 weeks off work to be at your beck and call because it will be a HUGE problem for you to look after your newborn when your stomach muscles are trying to build themselves back again. Is he willing to do that?
Okay, now I'll get onto you.
Congratulations! You're about to do the most amazing and extraordinary thing you've ever done, and every day you'll keep on telling yourself what an amazing miracle you've produced! When your bambino/a starts smiling/ eating/ crawling/ talking/ walking/ making jokes (this will all happen within 18months, believe me!) you will cry with joy and amazement at what you've achieved.
Are you feeling unsure or anxious about anything apart from the husband/ fanjo issue? I was TERRIFIED of the idea of giving birth between the years of 16 - 32. When I was preggers I went to ante-natal yoga (if you can find classes run by a doula I highly recommend it as she'll most likely give you great instruction and confidence on everything you need to know about giving birth). I also bought a hypnobirthing CD (you can get it from the NCT), which made a huge difference. My attitude to birth was transformed.
I had a 2 day labour during which I took 2 paracetamols to 'take the edge off' the pain (hahahaha! some midwife's suggestion!). I used singing (low humming, so it vibrated in my womb) to counteract the pain, then got to hosp at 7cm dilated and had about half a canister of gas and air before it was time to push.
I had special complications which led to my tear - most women will not have this. Even so, I was so high on endorphins that when I was in surgery I was still singing!! If I, with my former terror of birth, could achieve all that, no woman should feel too afraid to go for it.
You are wise to consider a water birth - I'm sure you know all the reasons why that's a great choice. Also staying on your hands and knees/ suspended from ropes, etc, are all great positions to ensure that your body gives birth more effectively. If you end up on your bum (like I did) it's bad for baby (cuts off blood supply as major artery to womb passes alongside the pelvis) and means your muscles don't use gravity.
I also had the most amazing birth partner husband, who deserves a medal and made the whole experience incredibly positive for me.
Your husband is unlikely to change his views. Much as it would be beneficial for him (and you) to witness the birth, if I were you I would (1) get some info from a doula about how important the emotional atmosphere is to the birthing woman; (2) armed with this info, tell him that he has made you very anxious about giving birth and you are concerned that his presence may have a harmful impact on your labour. Ask him to consider whether he is willing to support your decisions about birth. Tell him that if he is not 100% for your wishes (and it has to be 100%) that you will not allow him into the birthing room at the most vulnerable and sensitive time of your life. Give him time to mull it over. Be prepared to have a positive, close, supportive friend on standby (preferably one who's had a natural birth). If you can't find such a friend I'd definitely go for a doula.
This is an essay!