Help me save the Lion Heart

I just found two 3 days old kittens on June 13th in a plastic bag, with an outside temperature of over 30 degrees C.
I am in a country without possibility to buy all the stuff needed to make the kitten stay alive easier.
Please, I will welcome ANY advice on how to keep it alive. Please, make the advice as simple as "granny's" / I have no other but feed it on goat milk-luke warm water, a bit of yo and few drops of AD drops and olive oil.
It is a fighter, the other one died just a day after I found them (probably dehidration or hypothermia...)
It does not eat a lot and has problems with digestion, otherwise it fights... just asks for lots of warmess and love.
I keep in a box, warm it up with a bottle of warm water in a wool sock, unde a UV lamp to keep additional warmth (I just took some sick days to take care of it, also have 4 cats and a big dog)

Any advice / I will appreciate a lot!

Please help Lion Heart survive. Just don't tell me to buy an incubator or stuff similar to that since it is simply unavailable in my country. I am restricted to what I can do. As I write, it sleeps in the hood of my sports sweater.

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