Hello Speducator,
Thank you for using Apple Support Communities!
Based on what you mentioned, you have an issue with the word predictions. There are a few things you can do. As you mentioned, you can't create the shortcut with a space, so you can create "thanku" or "thankyou" as the shortcut. If you seem to have an abundant amount of words that you have trouble with on this device, you may need to start fresh and reset the dictionary. You will see this in Settings > General > Reset. This will eliminate most the learning your keyboard has done based on your style of writing or typing, and set it to default.
If you still have trouble you may be able to get help where you are when you Contact Apple for support and service.
Best wishes!