He will not really gain weight until he develops an immunity, then it will take him 2 or 3 months to reach size, I would say you'd be perfectly safe to eat it especially if its cooked throughly. But I would want to introduce it to your "Clean" farm or you will forever have problems
To answer your original question, just ask for their 16% grower, you can feed it to them their whole life and they will do well on it. As you learn about raising hogs you can deviate a little but when your beginning trust that the feed mill knows their stuff. Pigs are pretty forgiving, you can...
One other thing you forgot, Fodder is about 80% digestible hay I am not sure but we will say 40 (I think thats close), so if fodder is 2x as expensive per pound it is the same price to deliver nutrients to the animal
Wet feeding definitely helps weight gain if you do a little research, its not a significant increase but it is consistent and I would say it is definitely worth it if you are feeding by hand
Be careful with duckweed I have heard it has some natural growth inhibitors with a weird name like trypsin I think, do some research on that. Trypsin might not be the name of that. Soybeans have this or a similar growth inhibitor which is why they must be roasted before using
No it is not necessary to switch there are pro's and con's but over all the changes are unnoticeable it is really only worth switching for huge factory farms. You have it right on energy and protein. Switch over at around 150 pounds, if you choose to do so.