It sounds like you're doing most of the right things.
Don't get too excited about patents. If a major comany copied your design, could you actually afford to take them to court over it? If you're worried about the patent cost then probably not. The only value of a patent to you is likely to be that you can sell the patent rights to a company that could afford to defend them. It depends how innovative your idea is and how many different solutions there are to a similar problem.
Regarding other companies, it appears that what they are saying is that if you start manucturing that they will (or may?) buy them from you. So that leaves you taking the financial risk of setting up the manufacturing business. It reads as if your cost analysis may be on the wrong basis - for your problem the cost savings to the user are (sorry!) irrelevent, the question is simply: Can you sell enough units in the first year to cover your manufacturing start-up costs? Now you are in Catch-22: it is unlikely that suppliers will legally commit to buying products unless you have a product to supply, and you can't fund making products unless you have - at the very least - that binding commitment. Without it no financial institution is going to invest in you.
Probably your options are:
1. To persuade rich family and friends to invest in you (for most of us a fanciful dream) or
2. To persuade one of the interested potential customers to fund the business - but they will want to see a full breakdown of manufacturing costs, end product cost and when the first units will be delivered, they will also want to own most or (most likely) all the business.
Have you been advised on Non-Disclosure Agreements? Do you have one that you know is watertight?
Also, do you have a good understading of cashflow? It's the nightmare for start-ups: for several months you have to spend surprisingly large amounts of money with nothing coming in.
I've found that some of the best books for advice on start-ups around at the moment are tie-ins to the Dragon's Den series, for example "Your Idea Can Make You Rich" ISBN 0091909155. You may have to wade through some celebrity waffle but I've found the actual advice is much more clearly laid out than in many more up-market books.
Is your Private Messages turned on (doesn't seem to be)? If you turn it on I have a contact that may be of use that I can send you.
Andy Millar CEng MIET CMgr MCMIhttp://www.linkedin.com/in/millarandy
"The aim of argument, or of discussion, should not be victory, but progress." Joseph Joubert