First comment is that the best and most efficient day 2/5 exercise, squats, is in the wrong end of the session.
This is not only for the reason that squats are the best overall strength and muscle builder, but that they also are a technical freeweight compound lift, where you can move a lot of weight. And when you move a lot of weight, you want your body to be at its best.
The trouble in your plan is that you weaken the abs by working the abs first, then some hamstrings, abs again and then quads - and then you go to squats which work your whole body as a unit, not in isolation, but with weakened/fatiqued big main muscles.
When your weights creep up, consider splitting the day 1/4 into two separate sessions as well. As you lift heavier, you need more warm up sets, and more focus on the main lifts, so you may not have time to do it properly if the session is that stacked.
About the squat safety thing, so you dont have any stands which would catch the weight if you would fail? Olympic lifters dont use stands anyway, they just drop the weight behind them if they have to. This is actually pretty easy to do, but if you havent done it before you REALLY need to, it can go wrong and drop down your back, so actually it would be good to try it
Alternative is to buy stands... worth the investment!