Over more than 2,500 miles of Litchi waypoint missions, I’ve never seen this behavior of stopping at the waypoints that you have described.
I own a Fimi X8 which has a rudimentary waypoint planning facility, and that drone stops and pauses at each waypoint, consuming vital battery power. Never seen a DJI drone do that same stop and go shuffle though.
In a straight lines mission the drone stops at each waypoint. The only way to not stop is to change it to a curved turnes mission, however actions will be ignored.
That’s why litchi has introduced the photo capture interval feature which can be set to either a certain distance or time.
In your mission 5 waypoints for each row would be more than enough to compensate for the slope in the terrain.
For the above ground feature to work properly waypoint 1 has be as close as possible to the take off location.
Interpolate needs 2 waypoints to work. For pointing the camera down to -90d at the start of the grid you have to insert a waypoint with interpolate -90d BEFORE the waypoint that marks the start of the grid and only the first 2 waypoints have to be set to interpolate.