Recipe : Make my best sweet stout!

Make my best sweet stout!
The article is from : https://beerandbrewing.com/make-your-best-sweet-milk-stout/

grist :
4.8kg of Maris Otter
454g of pale chocolate malt(215L)
227g of Dehusked Carafa 3
227g of lactose

hops :
2 ounces(57g) of Fuggles at 20min
Ringwood yeast(Wyeast #1187)

When to add the lactose?
Flame-out of about five minutes left in the boil
(Stir in the lactose until dissolved, and then finish off the boil and chill as usual)

Key step :
Ferment cooler than usual for English ales(15 degrees celsius is a great starting point)
(OMG. It's not gonna be good until the next fall. It already hit up to over 20 degrees celsius in daytimes now.)

Carbonate? about 1.75 volumes.
(Cause slightly lower carbonation level will add an impression of sweetness)