I would think the best time with the cloves would be in the last 10 minutes of the boil...but be cautious I've heard a little goes a very long way in beer. I would reccomend you search "cloves" on this site and see what you come up with.
When it comes to addding additional sugars what I typically do, is brew, pitch yeast...let fermentation go for a day or two and then do step addtions with additional sugar. For example with my Belgian Golden Strong I will do as mentioned then at fermentation day 2add a lb of sugar then another lb at day three. The logic is this...you want the yeastie beasties to be awake and running at full speed before you completley overload them with so much food (sugar). I have had good success with this.
Please! This is supposed to be a happy occasion. Let's not bicker and argue over who killed who.