Splitting a long route on a day-by-day basis

My wife and I will be cycling around France during September and October. We've planned a 2600km route using cycle.travel but I cannot determine how to extract day long sections of the route for use each day. The "Split Route" feature in the web tool isn't what we want since that divide up the entire route a priori. We don't know how far we'll ride each day, so want to simply split out the section of the route for the next day, say 100km section. Then the next day, go back to the original full route, take our current position and split out the next 100km. And so on throughout the trip.

We want the short GPX tracks so that we can load it into Komoot for the day's ride. We've found using the cycle.travel iPhone app to be much more power hungry since it provides "turn-by-turn" guidance and hence keeps the GPS system always active, whereas Komoot only activates the GPS when the app is on-screen. The turn by turn feature is nice in a complex environment like a city but when we're riding in the country-side we don't need it and would like to save the power. 

Any advice on how best to do this would be appreciated. 

Adding point on route extends route back from the end

I was trying to create a route from Newcastle upon Tyne to Hull (part of a longer route) but wanted to follow more of the coast, as the Euro-Velo 12 route does, than what Cycle Travel suggested. Therefore  I added a point at  Scarborough which is on the EV 12 route. The Cycle Travel route maintains the original route to Hull but adds a section back to Scarborough. 

How can I adjust the route so that Scarborough is on the route to Hull not in addition to the route to Hull?I only have an iPad or iPhone to do my route planning, Using the tool on a desktop seems more flexible but not an option since I’m on a 4 month bike tour. 

Thanks.