I don't have any personal experience with this, having only one kiddo so far, but I am a midwife, so I've helped lots of people deal with nausea and hyperemesis.
First of all, I would advise you to think positive, in that pregnancies are often different, and you may not have the issues with this one that you had with the last one. So don't "borrow trouble" as my grandmother would say! If you take action now, you may very well be able to prevent or minimize the problems in this pregnancy.
In terms of you preventing nausea and exhaustion, a lot of that in early pregnancy is low blood sugar. I would suggest eating small, frequent, high protein meals. You should eat about every two hours at least, and have something with some protein in it. Chicken boiled in water with some salt, skinned and boned (have your DH do it when you're not home if the smell bothers you or have someone else do it!!) and put in pieces in the fridge is good. Sharp cheddar cheese cubes can be good. Almonds and other nuts can be good, or nut butters. Smoothies are good, you can put some protein powder or some egg powder in them. Don't eat a lot of refined carbohydrates, like crackers or pretzels or soda, because they will cause your blood sugar and insulin levels to go on a roller coaster and that makes the nausea a lot, lot worse. I would also definitely take a B vitamin supplement--there are some good lozenges that have B6, B12, and folic acid, and although I personally had trouble taking a lot of pills while I was pregnant I found that I could tolerate those pretty well. You can take 100 mg per day. I would also immediately find a practicioner in your area (I believe a naturopath is a good place to start) who can give you vitamin B6 injections. This has had really excellent results with a lot of women. Make sure you are drinking enough water, and if you can't tolerate it plain very well, a squeeze of lemon or having it really cold or even munching on ice can help keep you hydrated.
As far as your daughter, why would you not want to give soy milk because she's sensitive to dairy--there is no cow dairy in soymilk--are you concerned that she is allergic to soy as well? Also, some children and adults who cannot tolerate cow dairy can drink goat milk--have you tried that with her? I know that some people on here oppose giving nursing toddlers any milk at all as it can be considered a gentle weaning technique, but I also think that given the situation, you might want to keep your options in mind. I would try to make sure that the solids she does eat are as nutrient dense as possible, and maybe experiment with different foods to see what she likes. I try to feed my toddler frequently, because it's hard to feed them too much at one time at this age and they stay happier if they graze throughout the day rather than eating three meals. I give her snacks often (she often asks for them) and then feed her when I eat, and I make sure she gets a good snack before bedtime. Dr. Sears has recommended preparing a "nibble tray" for toddlers that you can keep on a low table or otherwise accessible to them throughout the day--a muffin tin or ice cube tray with toddler sized portions of different foods like crackers, veggies, dips, fruit, etc. I can't implement this because we have two dogs and it would become the doggie snarf-the-whole-thing--down tray!! But I do try to keep things handy and feed her throughout the day every couple of hours. Sometimes it's just a few bites of banana or a little piece of whole grain cracker or toast with some goat cheese. I still nurse during the day too and nurse her to sleep, but I find that if she doesn't get a good sized snack before bed she nurses, goes back and forth from breast to breast and doesn't get satisfied and this will go on for a loooong time, and it's frustrating for both of us. Often after this goes on for half and hour she will sit up and ask and sign for food. I mean, I do what I can to improve my supply, but I'm only human and I have my limits. I have started giving her a little goat milk before bed, and she loves it and will drink a glass of it, then still nurse well on both sides.
Do you have a LLL meeting near you? Maybe a LLL leader could give you more support and practical advice. Hope this helps some, anyway, and congratulations on your pregnancy and good luck! (Also, congratulation and kudos for nursing to 18 months--whatever happens, your daughter is one of a tiny fraction of the baby population who has been so lucky to be nursing this long!!!)