Need detailed help on how the Apple Business Program works I want to ask a question about the Apple Business Manager program, but I need to give some background.

At my job, we are an iPhone Dev shop.  We build our code using ionic/cordova and then compile it down to scope, which I build.  Here is the difference.  We currently use Apple’s Enterprise License to build our product, and then export it to a third party site (NOT the Apple App Store), to get around the stringent Apple review process.  It is what it is.

Ok, so now with WWDC19 (https://developer.apple.com/videos/play/wwdc2019/304/), Apple has REALLY tightened up the leash for the Apple Enterprise Program.  Both our new clients, plus my dev team’s request for a new Enterprise license (all with unique DUNS numbers), were declined, as Apple is pushing us to to the Apple Business Manager.  

I looked at the link found above, but it is rather high level and “assumes” I already have an Apple Developer account and are using Apple Connect.

In short, I desperately need some help.  Before I loose rep points, let me say that I have searched the web for the steps, and nothing quite meets my needs.  

Here is my understanding (please help and don’t flame me).  I am not a novice. I just come from an android background).

1) In order to use the Apple Business Manager, we first have to build and publish the app (via Xcode) to Appleconnect to have the app reviewed.

In order to do this, I need the followin:
1) Valid appleid and an enabled $99US Apple developer license (and accompanying provisioning profile).
2) Tax and Billing (credit card info) for my Apple Id in Apple Connect account.
3) I build my app using Xcode 11 using both my valid apple developer license + provisioning profile and team account.
4) Once built, I distribute the app to the AppStore.  When prompted, I DO NOT export it locally.  I upload it directly to the AppConnect portal.  Successful upload assumes that all the previous billing stuff (in #1) has been approved and validated.
5) This begins the Apple review process. 

Is this it?  I DO NOT want this app to go onto the public app store, as it is a B2B app (meant to house sensitive client data).  Once the review process has completed, (for lack of a better term), how do I get the app to the Apple Business Manager site of things?  

I did some googling, and there is mention of a VPP program.  So once the review is over, do I get the option of getting a VPP link? Do I then have the option of providing this link to Apple Business Manager, or can I provide this link to our 3rd party?
The steps you describe are correct, yes. There's however no need to do it manually like you describe - you can just choose Distribute in Xcode to automatically send your archived build to Apple. Just like you would if the app was going on the App Store.

The difference between putting the app on the App Store, and doing what you want, is simply this one step: On App Store Connect in the "Pricing and Availability" tab for your app, you have to select "Available privately as a custom app for business". This marks your app as private and makes so that the public cannot find it on the App Store.

When you have selected that it is a private, custom app for business, you'll be prompted to provide the IDs of the customers you want to be able to get the app. When you publish your finished app, those customers will see it in Apple Business Manager.

The customer will be able to buy the app, and install it on devices using either MDM (centrally install the apps) or using redemption codes (where the enduser enters the redemption code on the App Store).

There's no special "link" that you need to provide to your customer.