1-He filled his stomach ..means he will not ask for more , yes he has شبع 2-إنه لمن دواعي سرور this is the only use for دواعي in the modren standard Arabic دواعي are that things that (invite or make) تدعو here literaly the meaning is : "surely it is one of those things that make me happy to meet you here and share you ..etc" it is = إنه لمن the letter لـ is used for affirmation ....I translated it into "surely". من = of ....> in this context it means "of".

لـَمِن لام التأكيد+حرف الجر من surely+(this is) + one of those things that make me happy.