If you're having problems with audio playback, this signifies an issue with your audio I/O setup and/or your audio device driver.
However if you're able to record, but not able to playback, perhaps your playback Output Channels are not set.
Open Song Setup in the Preferences menu to and select Audio I/O setup, there are two tabs, one for input and one for output. Be sure to add mono or stereo buses for your device. Then once you've added your channels, open the mixer and make sure your master playback channels are assigned to the master audio output or whichever channels your speakers are attached to.
As for the waveform draw, the waveform on the arrangement page is meant to be a representation of the actual audio. Double click any of the waveforms to open the editor to see it in more detail.
If you require better detail on all your waveforms, perhaps consider adding an external monitor to your MacBook Pro like a Thunderbolt 27" Display, then using the magnify sliders for vertical and horizontal you can adjust the zoom levels to see the waveforms more to your liking. Even with a 27" monitor, the more tracks you add, you'll end up with the same issue as you did on your laptop screen.
