Coolant mixture

Do you mean 60% water 40% coolant or the reverse? What is the reasoning for the 40%? 50/50 is the common mix used, unless you are in extreme cold, then they might go to a 60% coolant mix.
Either way you just start with a gallon container. Mark the spot for 1 gallon as 100, There are 128 ounces in a gallon. Every 10th of a gallon is 12.8 ounces. If you wish to be precise take some water, measure out 12.8 ounces, pour it into the jug and make a mark. Keep adding 12.8 ounce measures and marking them until you have made 10 marks.
Each mark is now 10% of a gallon. For 40% you would add coolant to 4 marks and the water for the other 6. Or just do like most people do. Start with an empty cooling system, dump in 1/2 gallon of coolant, then 1/2 gallon of water. Then combine the rest of the gallon of water with the coolant to make a 50/50 mix. Repeat with the next gallon of coolant and water. That should give you an almost full system and 2 gallons of 50/50 mix to finish topping off the system.

Okay, the 40% would be for a warm climate that doesn't freeze with the 60 being for a cold area. 50/50 sets in the middle and is easier to deal with. The thing with mixing coolant is that you don't want to run straight water in the system as it boils faster than a coolant mix and doesn't transfer heat as well. However, you also need water in the mix as straight coolant with no water is actually worse than running straight water. 50/50 will usually put you in the middle with protection down to 30 below zero and around 250 above zero. The lower coolant level mixes don't increase the boiling point but you do give up the low temperature protection.
Unless you live in an area that never freezes I would opt for 50/50. Easier to mix, easier to top off as it's what all the pre-mixed gallons are as well.

There are multiple oils that meet the 502 standard. These are just a few. If you want more just search online for "oils that meet Audi/VW 502 standard" There is a TSB from Audi as well search for Technical-Service-Bulletin-1.22.2018 Should be one of the top entries.

Castrol Edge A3/B4 SAE 5W-40
Castrol Edge Turbo Diesel SAE 5W-40
Castrol GTX Magnatec C3 SAE 5W-30
Castrol Magnatec C3 SAE 5W-30
Castrol Magnatec Diesel B4 SAE 5W-40
Castrol Magnatec Professional B4 SAE 5W-40
Castrol Magnatec Professional C3 SAE 5W-30
Castrol SLX Professional B4 SAE 5W-30

Chevron Havoline Ultra S SAE 5W-40

Fuchs TITAN GT1 SAE 5W-40
Fuchs TITAN GT1 PRO FLEX SAE 5W-30
Fuchs TITAN Supersyn PLUS SAE 5W-40

Gulf Formula ULE SAE 5W-40
Gulf Formula ULE SAE 5W-30

Mobil Super 3000 XE SAE 5W-30
Mobil Syst S ESP SAE 5W-30
Mobil Syst S Special V SAE 5W-30

Pennzoil Platinum European Ultra Diesel SAE 5W-30
Pennzoil Platinum Low SAPS SAE 5W-30

Quaker State Q Diesel Plus SAE 5W-40
Quaker State Q European Engine Ultra Diesel SAE 5W-30
Quaker State Q Synquest Low SAPS SAE 5W-30

Quantum Quantum PD Diesel SAE 5W-40
Quantum Quantum PD Diesel SAE 5W-40
Quantum Quantum Platinum SAE 5W-40
Quantum Quantum Platinum SAE 5W-40

Shell Helix Diesel HX7 AV SAE 5W-30
Shell Helix Diesel Plus VA SAE 5W-30
Shell Helix Diesel Plus VA SAE 5W-40
Shell Helix Diesel Ultra AV SAE 5W-30
Shell Helix Diesel Ultra VA SAE 5W-30
Shell Helix Ultra AX SAE 5W-30

Valvoline DuraBlend Diesel SAE 5W-40
Valvoline SynPower HST SAE 5W-40
Valvoline Synpower MST SAE 5W-30
Valvoline SynPower MST SAE 5W-40

Don't really pay attention to sizes, I just look and grab the wrench that fits.

As for the transmission fluid, the first thing you need is the special tool used to check/fill the fluid in that transmission. Also you need a way to get under the vehicle with it level. No jacking only the front end up. A lift or pit is the best way. There is a check plug in the rear outer corner of the transmission pan. You remove the plug and see if fluid comes out. With the car level there should be a bit that has gotten into the tube and will drain out and then it will stop. Next you install the fill tool. Then add a small amount of fluid until it drains back out. That means it is full.
To change the fluid you need the same tool, however you remove the inner overflow tube that is inside the check plug hole in the pan. Then drain the fluid and reinstall the tube. Then add three liters of fluid using the filler tool. Then check the level after starting the engine and running the transmission through all of the gears. Add if necessary.
However this only replaces three liters out of the seven in that transmission.
For a better solution you may want a dealer or good VW shop to flush the fluid. That would change all of it and they should have the correct fluid on hand.

VW G 055 025 A2 or equivalent.