Ken
On the 1782 I had, I would heat it till the light went off then turn the key to the off position and repeat the heating two more times then turn it to start. In your vid I noticed you only heated it one time. I also put a heater blowing under the engine for a couple hours before I tried to start it. On my BX the glow plugs heat as long as you hold it to the heat position. On the BX I heat for about 15 seconds in cold weather, about 8 in warm weather. You also said you have 2 batteries, maybe one of them is not so good?
The slow down may be the hydro pump starting to make pressure with cold oil.