Yes, it is safe to add "even" or "much" before, they are adverbs and provide emphasis.
As far as success vs successes this just depends on what you want to say.
Success can be defined as:
- the fact of getting or achieving wealth, respect, or fame
- the correct or desired result of an attempt
So you can either use success which would imply the first definition. "May you achieve a greater overall sense of accomplshment/wealth/fame etc."
or with the successes which would imply the second definition: "May you achieve a series of desired outcomes from the many things you attempt in life"
So if you're wishing an overall sense of success you'd leave off the plural. If you want to emphasize success with individual events or tasks they may undertake then use the plural.