OK, for what you want to do, Old Town is a good location for walking in the area, plus access to public transit.
SeaWorld is a short bus ride from Old Town on MTS Route 9
2. The San Diego Zoo would be the San Diego Trolley to MTS Route 7.
3. Aquatica San Diego (former Knott's Soak City) is now operated by SeaWorld, and is located in Chula Vista, so you would have to drive to it. It is only open on Saturdays and Sunday in September.
4. Beaches, MTS Routes 8, 9 and 30 all go to the Pacific Beach area from Old Town, Route 8 goes through Mission Beach.
5. Easy Trolley trip to Gaslamp Quarter and Seaport Village., Old Town is within walking distance.
6. You can get there with public transfer, with a transfer. But I much prefer the Pacific Beach area, especially for bars and restaurants, a lot more to choose from in the area.
7.Old Town is a great place to eat and drink.
Also, the Old Town Inn offers free parking on their property, which is important if you will have a car.
Hope that helps.