If your temp is set to 300c that translates to 570f, which is probably too hot. 188c = 370f and 232c =450f You should be able to switch your mod from Celsius to Fahrenheit if not run it between 188C and 232C and you should be OK.
What are you looking for in a tank? Are you planning to build your own coils? Do you want a tank that comes with prebuilt coils? What about a tank that has both? Mouth to lung? Direct to lung? How much juice capacity are you looking for? Are you hard on tanks so it needs to be something that won't break easily? Do you want Pyrex instead so you can use any kind of juice in it and not have to worry about tank crackers? So many questions....
Doesn't add up
40W? 300*?
if you are vaping temp control then those settings are a little wonky. Temp control is prob shutting down that coil before you're getting any vape. If I were you, without changing your nic, I would bump the temp up to 350 and drop the wattage to 15 or 20. See if you notice any change.