+1 on the RWS Model 34. I have the .177 version with scope and over 15 years have bagged around 80 rats, 1/2 dozen squirrels and she still shoots like new. A fine air rifle.
RWS Air Rifles and Pistols - Model 34, 48, 52, 54, 350, 460, LP8, 5G
As for squirels in the tomatoes, a simple protective netting might be more effective because it is on duty 24/7. These are a must in the grape vineyards around here to keep the birds and squirrels out of the fruit.