Wow, what a discussion running here 
Thorsten, let me tell you two things which I learned over the time. Not about or with Xojo, but in general about being an entrepreneur and developer.
FIRST: There are cultural differences between american people an german (and may be others). It is simply normal that you hear promises from american people. They simply want your money. Which is OK if you know that and act always with this in mind. So you go and make extensive tests with the stuff you are going to buy. EXTENSIVE. And if the test worked, you pay. If a german car is sold and the wheel cap is missing or crappy, everybody complains about that. If an american car is sold and the car is complete crap, you get shown the wonderful wheel cap by the sales people. That’s the way it is. And it is not going to change in the next time. On the other hand if you try to sell software to them, it is VERY had to convince them - simply because they are used NOT TO BELIEVE. So they invented the test drive. Cultural issue.
SECOND: What I learned from Caesar: “Divide et impera”. If you have code with hundreds of megabytes something is going wrong - or wild if you want. If you write software you will DIVIDE bigger chunks into smaller parts and define some very clean interfaces. Code of this size is not maintainable. It is hard to document. Did you have a look at the Workers?
So I have to disagree with your meanings here. We used Clarion and WinDev before we swapped to Xojo - and it was not better with those two. It was WORSE then Xojo is today. We developed several projects in Xojo now and everything worked fine. Of course problems, but all either worked around or solved by the people in this and the Xojo forum. Mac, Windows, Linux and iOS - all up and running.
I feel your deep frustration about the swamp you are in. And I must admit, I do not like languages which use brackets and semikolons. I like your customer who wanted a basic code. I would NEVER use Java because of the license policy of Oracle. You will see: your customer will pay the money to Oracle and not to your company. What about that?
And so on. I hope you stay healthy in those difficult times. I do not post very often, but your text touched something in me, because I experienced similar situations looong time ago. Thank you for being so emergent.