To know how much time need to the next feeding just do the next. Look the Food number# then that number multiply x 10, then divide /3600 and the result will be the number of hours until the next time need to be fed. F.E the food number is 1850.5 1859.5x10=18595 /3600 = 5.1 hours
A fire wyvern is one of the best you can have because they are resistant to fire damage so alpha wyverns are much easier to kill same with all the wyverns they can't hurt each if they are the same element but the bite attack still works on all wyverns keep this in mind
Killing an alpha fire Wyvern is also another way to get milk. When killed they have 50 milk in their inventory and a nice trophy to mount on your wall. Alpha wyverns will always be fire and they place a sick looking Wyvern glove skin in your inventory when killed.
If you want to hatch an egg id suggest building 4 thatch foundations with greenhouse walls and 4 thatch ceilings then use 5 fire places to heat the eggs its easier to farm the resources for them works 100%