don't bother with the boat,
You can fly from the USA to Europe with ferry tanks, which you will need anyway.
an IR would also be helpful, but not essential.
lots of people have done it, and several pilots have also flown to South Africa.
Ignore the nay-sayers -- if you got the money, the dedication that you need to get the planning perfect, and the time, go for it. I bet you'd find a third person to share the costs. But try and keep all crew as light as possible - you'll need a lot of fuel.
I flew a R44 from the UK to Australia 10 years ago, and I loved every minute of it. Well, almost every minute.
Big Ls