Very normal to salivate a lot. As for fingers, he’s discovered them, and are probably exploring them. When my LO got a bit older, she changed from sucking fingers to picking up everything else and putting them in her mouth. But recently at around 7-8 months, her fingers sometimes go into the mouth again.. this time, I think it’s because her gums are uncomfortable with the teeth coming out soon
Not a sign cause mine have been doing so for a 3 weeks.. teething usually last few days only