I'm glad you dropped the dose back to 1.5 u after that lime green yesterday. When you need to change dose again try hard to eyeball 0.25 u fractions instead of 0.5 u. That's too large a change at a low dose range like yours.
Yes, giving a small snack around +2 can sometimes help to reduce the drop rate. However, Vetsulin's action contributes to that issue. It has a fairly fast onset and can drop BG fairly low from high PS numbers. Controlling the drop rate can be hard with Vetsulin. The snack shouldn't have much effect on the nadir. That tends to fall in the +4 to +6 range for Vetsulin, although it can move around a bit. Feeding too much food after the mid point of the cycle can sometimes shorten the duration of the insulin. Sometimes a dose that's too high will give longer duration.
It's best to assess the dose by seeing how low it drops the BG. Your goal should be the low 100s on an AT meter - high 90s at the lowest. You need a safety cushion like that because of Vetsulin's aggressive action. Try to avoid dosing according to the PS number because they can be high with Vetsulin.