Originally Posted by Alec300SD

First question: In cold weather glow plugs need to be healthy, engine needs to spin fast when cranking, higher cetane fuel helps, a warmed up engine helps, and you need good compression.

Compression is probably fine with your low mileage.
Engine can spin faster with good battery.
Clean starter circuit electrical connections can help.
Lighter viscosity synthetic engine oil can be used.
You are already plugging in the block heater.
Cetane boosters can be used.
Glow plugs may need replacing...or longer glow times (double or even triple glow).

Second question: Power Service Diesel 911 (red bottle) is designed as an emergency de-icing product when water has frozen in your fuel filter and the fuel is not gelled.
Carry a bottle for emergency use but don't use it every day.
Anytime, but especially in the winter you can use the white bottle of Power Service Diesel fuel supplement to boost your cetane and prevent gelling of your fuel. Available at Walmart and other vendors.