Take this all with a huge grain of salt since I play PL almost always.

On hand #1 - you've got the high all but locked up. I think it's a matter of balancing the concern that somebody will catch the low with getting more money into the pot. I think the 3-bet is probably the wrong play though. The BB ought to have a low draw so why not try to drag along the others to get more money into the pot and the possiblility of extra bets on the river if two players catch their low?

Hand #2 - I've never had a good feel for when to value bet and when to check. I probably would check/fold this river since it's a run at what could be a dry pot, the all-in player might have the flush.