1) The reset time means that if you don't activate the macro for that many seconds, the sequence will go back to the first spell. If you keep activating the macro, it will keep trying to cast the next spell in the sequence, and go back to the first spell once it reaches the end of the sequence.
2) Putting numbers instead of spell names in the list of spells will not add additional delays -- but it will try to use the items equipped in those slot numbers. The first line in your macro:
Code:
/castsequence reset=1 3,5,3,1,Fireball
Effectively translates as:
- On the 1st press, use the item equipped in the shoulder slot.
- On the 2nd press, use the item equipped in the chest slot.
- On the 3rd press, use the item equipped in the shoulder slot again.
- On the 4th press, use the item equiped in the head slot.
- On the 5th press, cast Fireball.
- On the 6th press, start again at step 1, and use the item equipped in the shoulder slot.
- If at any time the macro isn't activated for more than 1 second, the next press will start again at step 1.
Unless your shoulder, chest, or head items have "use:" effects, then the first four presses won't actually do anything, and if you stop pressing the macro for more than 1 second, it will start over with trying to use the shoulder item. This is why it seems "random" as to whether your macro casts Fireball.
3) It sounds like you're trying to write one button that will use all of your abilities in the correct order at the correct times, which is exactly what Blizzard doesn't want you to be able to do -- that's why there are no macro conditionals for "if this spell is on cooldown cast X otherwise cast Y" etc. and no way to write a macro that you can keep pressing that will only cast spell X every 3 seconds, spell Y every 11 seconds, etc.