Roxy, i agree, there is more to learn when betting baseball than any other sport....I will try to briefly answer your question here, based on my opinion, some others may have better advice for you....
Atlanta is the underdog in the game, hence the (+) money on them, if i take them on the runline, i get +1.5 runs, however it will be high juice, and if i think they are gonna win, no reason to lay that juice, only in a 1 run loss, would it have been beneficial....Now some books offer alt runlines, and I could lay -1.5 with Atlanta, and it would be a greater (+) price, however, i am just playing for Atlanta to win today, not by at least 2....
On Houston, they are a big favorite, and i look for them to win by more than 2, therefore i played them on the moneyline, and added a smaller play at the (+) money on the runline.....if they win by 1 run, i still come out ahead, if they win by more, i come out more ahead......Often if i REALLY like a team, and they are a big fav, i will play the runline only, to absorb some of the juice....I prefer this on the road however, as a home team its a little tougher, because unless its a walkoff homer, game ends when winning run is scored in late innings....On the road, they keep going, u can get that 2 run cushion...
However i like Oswalt, do not like Milton, therefore i played the runline as well with Houston..........Same deal with Florida, i really like them in the game, but didnt want to lay -200, so took a shot with runline, even though they are at home...