Lacto geek, reporting for duty! Ok, I'm going to keep this brief, because I've been sampling tonight. But lacto dies around 130°F. So does yeast. So like @loopie_beer said, pasteurize at 160-170°F. It's MUCH higher than the temps at which any microbes can survive. So you're safe. As long as you have a pH drop within 4 days. Or start making alcohol. With goodbelly, it won't be an issue.
If you boil pils for anything less than 30 minutes, you risk DMS and a beer that tastes like creamed corn. Keep it under the temp to convert SMM to DMS, and it's not a problem. Go over that temp, and you had better boil for an hour.
And oh, 1 carton of goodbelly is enough for 10 gallons. Should be done in 18-24 hours. But no harm done by pitching extra. Lacto is self limiting. So go with 1/4 carton for 2 gallons. Or heck, pitch the whole thing. No harm done. Mango flavor is pretty flavor neutral. It'll be great.