Hi Jason,
Looking at your posts, I get a feeling, that you have put up extraordinary efforts in building this PID Controller, and I congratulate you for it.

But as many other members have mentioned here; (I think) You have taken an improper route to design this product.

Like my father said:
"For a business: You can design the best product in the world, but if there is nobody to purchase it or use it, then that product and your efforts are useless."
Bottom line is you should build a product that is sellable.

First study, what is available in the market. Read its specs, features, (don't forget Optional features), prices, look and finish of the product, reliability of the product, After sales service support, their Infrastructure, What other models of the same product are available, etc.; All this compared to the cost of the product.

Nowadays, customers asks: what optional features are there in your product?
So it is taken for granted (and assumed) that your product has to working 120% better, no downtime, no development changes once the product is on the production floor.

Study and think how you can cope up with these in your product, and then start designing your product.

Don't get disheartened: My experience says that you have customers that require products of various grades and quality. Even chinese products are sold here in India, solely because of low-cost. people know that if it works for even a day, they will purchase it, because it is dirt-cheap, and wasting that much money will not cause much harm.

If the above seems complicated to you, I will explain with plain and simple example:
If you have to purchase a TV for your home; What are the things that you would look before purchasing a TV? You never ask what ICs it is using, you talk about the "features" and "Specifications".

You find all types of TV in the market. Some are hot selling items, some are sold in very few quantity..but they do get sold...if they hadn't, you would not have seen them in the shop at all.
A quick look will tell you there are various grades of TVs: LCD, CRT Based, FlatScreen, etc. with their own price tags with about 0 ~ 20% deviation within each catagory.

So select the grade in which your product falls in.
What features are standard for this product range. What more you can give, so that customers will come to you, and at what price, what after-sales-support, etc.

Remember:
Product Technicalities : 30%
Non-technicalities: 70% :market research, production planning, cost, marketing, etc.

You have done your 30%, what about the rest?

There is a lot more to say, but it is awfully a long post, you might feel asleep...so stopping it here.
Thanks for reading it.