Hi Karl.
I had the same problem (porting one App from Android to iOS). The Android App was written with B4A.
In my experience, the conversion from B4A to B4i has been simple, 'cause B4i is VERY similar to B4A.
There are some minor differences (the OSs are really different), but the forum can help you to find a workaround for that.
I purchased B4i and rent the remote compiler for one year, waiting for a "personal Mac" to use on local LAN.
Now I have the MAC and use the local compiler, but the remote compiler has the advantage that can be used as a host for your App while you are distributing the App to your beta-testers. In fact, when you have your App working, you can ask your beta-testers for their device's UDID and add them to the list of users in mobile_provision. Then, using the remote builder, you can store your App to the B4X secure server (https). After that, your beta-testers can install the App simply connecting to a specific link with their iOS device. This feature is really useful.
Well, that is the easy part.
The other part is the Apple side.
You MUST create an Apple Developer account (here in Italy is 99 Euro / year) to start working.
If you have a MAC computer, you can use the builder supplied by B4i, installing it into the MAC, otherwise, you can use the remote builder (this is a pay service) running on B4X server (internet connection required).
Local builder (on MAC machine) works as java program, so you must download and install the java builder (free).
You also must have an Apple device (iPhone or iPad) running iOS 7 or newer, to test your App.
I tried the simulator on the MAC, but is considerably slower than the B4i bridge installed on the real iPhone / iPad device.
The B4i-bridge is equivalent, as function, to the B4A bridge. If your Android App has been written with B4A, you know it.
The final part, when your App is finished and your beta-testers sent you a positive feedback, is to publish to Apple Store.
I must stop here, 'cause I'm just arrived to this step !!!
Hope this brief information will help you...