Chris_15
Q1: Yes, by “topping up” you do this with the same package size you already had.
Q2: No, you’d need to cancel your current 1000 package and then purchase the new higher value passage. According to the official rules, a cancellation is only possible “by end of the travelcard month”, whatever that means.
But since that online “top up” process is still quite new and before it was made available, cancellations were possible on shorter notice, I’d suggest to go to a staffed SBB counter and see whether they (still) could accelerate things a bit for you.