I totally get your concerns jelly and don't think you are coming across negatively.
Re I am more concerned that they have never spent more than 10 hours together and the majority of the time they see each other every 3rd week for about 5 hours. It isn't about the not sleeping together/living together, more the quantity of time and worry if they are actually a match.
Can you encourage or suggest she does some project with him, something that means they will be together a lot more. A church renovation or short term mission trip? Be careful what you wish for, she may ditch him and end up being a missionary, if you suggest somewhere like France for mission she would be your door step!
DH nd I dated for 2 and half years before a six month engagement. We did go on holiday without sleeping together, it's not easy but is do-able. She could go interai;ing or the modern equivalent of it, staying in YHAs etc. I think she needs to see him in a variety of situations.
Could you suggest a family hiking and youth hostel holiday together, all the family, to get to know him, or rent a cottage (separate rooms if they want) for a family holiday? If you go out of season it would be cheaper and you and your dh could pay as a treat. Seeing him day to day in a home environment you may discover why she loves him. In many ways the more basic and simple the better! No internet or TV, wintery walks and board games in the evening! Either you will see how lovely he is or she might see how unlovely he is!
I agree the being sorted is the most worrying bit and I think only part of that is about being religious.
Aside from the religion what else is he, are they, into? When you are young and a Christian it is easy to be quite 'dogmatic' or 'on fire' I know I was. As a 50 something I am much less so but I hope just as faithful. I know others who have changed and developed. The fact it is a C of E church hopefully means it won't be teaching anything weird (I hope) and they really should do prep classes. Good luck. To all of you.