Who can field "Bg (O)"?
It is not clear at the moment! But it is likely that all Hellenistic armies will be entitled to Irregular Baggage (O). It will not be certain until List Book 2 is published, and we do not know when that will be.
The general rule is that all armies can field 0-2 elements of baggage per command. For most armies, baggage is irregular. In the only published list book, the only armies which got regular baggage were Byzantines, some Chinese, and Koreans. Again, for most armies, baggage is (O), which represents tents. Usually only nomad armies get Baggage (F), which represents pack mules and horses. A few armies can alternatively get Baggage (I), which represents unruly farm animals.
The advantage of baggage is that it increases command sizes very cheaply.
How many points is Your army?
400 points.
Yes, Salaucids are similiar to Macedonians. They only get few extra "asian" element types: chariots, elephants, camels etc. I will try to use them after few games.
One little hint. If you intend to use Scythed Chariots, also purchase the "Unusual Weapons" stratagem. This allows you to deploy them after your opponent deploys. If the Scythed Chariots are part of a command which deploys wide, you will have a lot of options as to where to deploy them.
Why did You take mounted general for Your Pk block?
Two reasons. Firstly, according to the list, if I wish to have a Pk general, I have to have two of them, and I do not wish to do that. Secondly, he is a useful movile reserve in case the enemy breaks through the phalanx.
Seleukos I Nikator or any other seleucid general was not a brilliant one
Antiochus III is, from 220BC.
I like Your Command 1:
Superior LH, few Kn, some difficult terrain specialists.
Yes, in my opinion, the Kn (F) are not a powerful enough attacking force by themselves. In your army, you support them with elephants, which is good. I rely on good support from the LH (S), and Brilliant Alexander. The Ax (S) are useful general purpose troops, and Ps are useful for skirmishing, and for dealing with elephants.