As Allan said, tyres are your main issue here.
Run new 4wd cut staggers on full sized rim, or 2wd mini spikes on full 4wd rim, with inner and outer spikes removed. These will give you much more steering.
I thought 2wd cut staggers were horrible to drive.
Have you tried minipins all round on the astro? front is tuned by removing spikes.
Also how many shock inserts are you running on the front? Too much front droop (or front lift on power) takes away on power steering. You'd normally be running 5 insert washers on the front. This is more than shown on the kit build.
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