Read this:
Spoiler: Read this
I think you are asking to much to try and calculate the distance you want to travel.
I would break it up into smaller trips.
When you reach the first point then load the next one and so on.
Test the shorter routes to see if they calculate.
Or you might need a different Openstreet map there are many out there.
Also like I said before try OSMAND+ too.
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