2002 Honda Civic P0300, P0301, P0302, P0303, P0304

If the timing is off, you would normally have low compression all across but I am not sure how the leak down test was done so there could be some error while perfoming it.

Checking the timing belt is the easiest and fastest way to avoid expensive and time consuming repairs so why don't you perform it first?

While you are at it, with the pistons NOT at TDC and the valves free, tap the valves to let them seat correctly, sometimes dislodged carbon can cause leaks as the valve are not able to be seated fully.

If the timing belt installation is correct and you still have leaks at the valves, then a valve job would have to be performed as you mentioned checking the valve clearances and cnfirmed them to be correct.