Welcome (back) to the world of raging hormones. What you're feeling is totally normal! It's always hard to imagine adding a baby to the mix, especially when you are undergoing so many changes (new marriage etc.). It's hard to imagine that it won't mess up your relationship with your daughter - but it won't. It will change it, but not necessarily for the worse!
You're not that old. You are 35. You are "seasoned"! I just read that Laura Linney (the actress) gave birth at age 49!!! What you have added in years you have also added in experience, wisdom, and perspective. You will not overreact to a slight fever, you know how to swaddle, you know how to bathe a baby, you know that solid foods and potty training and sleep training come in their own time - all the things you didn't know when your daughter was an infant. You are not more likely to have complications now - you are putting more pressure on yourself perhaps because you are more aware than you were at 24. I was older than 35 when I had my child - you can do this!
The wedding can be scaled back or changed to make it manageable - there are zillions of pregnant brides and their weddings are just as beautiful and meaningful as the non-pregnant brides!
My only concern here is that you seem to feel you have the entire responsibility for housekeeping. I don't know if your fiancé is averse to housework, or if your standards are too rigid for your lifestyle or for anyone else to participate. Even the word "help" means it's all your job to supervise. Why is that? You both work full time and you have a tween daughter. You say your fiancé will be a good dad - doesn't that include bathing and picking up toys and doing grocery shopping and cleaning bathrooms so that his child has a good environment and a hands-on father? Will you not allow him to participate fully as a husband, father-figure to your daughter and ultimately father to the baby? Or is he refusing?
What can you scale back, starting right now, to make things easier? Your daughter can be in charge of her own room (close the door if you don't like how it looks). She can put her own laundry in the washer, sort and put away the clean stuff, and hang up her worn but not dirty clothes for a second wearing. She can put her dishes in the dishwasher. Can you get a couple of baskets for the high-clutter area of the house, and just have everyone take 5 minutes a day to pitch things into a basket labeled for each person? Then whatever is missing needs to be sought out in the appropriate basket! Can you eliminate some jobs? Beds really don't have to be made every day, Sunday can be a cook-for-the-week day where you make 5 meals out of some basic ingredients that cook simultaneously (Rachael Ray and others have whole books devoted to this) and it can be a family bonding experience.
Yes, a baby will take time away from your daughter, but isn't this true of every family who has more than one child? Aren't there offsetting advantages? For example, your daughter will see how much work a baby is and perhaps be less likely to have her own baby as a teen, and ultimately be better equipped in 15-20 years to care for her own child. You can still have time with her by leaving a baby with this great dad you're marrying! She will always be your first child, but she's also growing up and will be heading to high school and beyond before you know it.
If you and your fiancé can do some good negotiating, either together or with a trained counselor, you can probably work out a lot more compromises. You are entitled to your fears and he needs to step up to try to understand them and help you get through this period of adjustment and hormonal upheaval.
Good luck!