ABQ to Tower Building & Rental Allowance

If you look at the "Living in Aramco Residential Communities; Living in Abqaiq" forum, you will find lots of discussion about the commute. The most recent is:

viewtopic.php?f=75&t=92196

There is also some discussion about the idea of finding accommodation in Al Khobar.

To answer some of your other questions, it would be extremely difficult (if not impossible) to arrange accommodation outside Aramco before arriving. As far as I know, to rent somewhere, you need to have an iqama which you won't have until at least a couple of weeks after you get here.

Yes, you have to apply for the rental allowance and again, as far as I know you would not be able to do that before arrival.

You should also bear in mind the 90-day probation period. Although it is rare, some people do not make it beyond that period (usually based on their choice but sometimes at the company's). Last time I rented a place in Al Khobar (which admittedly, is over a decade ago) most rental agreements involved paying a year up front, so I'm not sure I'd be comfortable about putting down a whole year's rental money too soon after arrival.

I would recommend getting here first, moving into the company-provided accommodation in Abqaiq and then taking some time to assess the situation (difficulty of commute etc) before deciding to look for rental accommodation in Al Khobar.