The rule of thumb is the depth should be at least 1x the fish length at all times. So if I planned to house an RTC for life, the worst case scenario it will grow to 4', so I'd go with a 4' depth.
Both silver and Asian aro will be preyed on by the RTC sooner or later, especially the Asian. Even if the RTC will have failed to swallow them whole, the arowana may die from wounds and stress. Speaking from experience. See my thread on silver arowana in the Arowana Forum.
TSN may or or may work out but could be tried. You said you have already lost one TSN to your RTC. Perhaps need to start with a bigger TSN but not too big that it can eat the RTC.
IMHO 10x10x4 is not enough to house an RTC for life (20-40 years), if it reaches 4'. My 4500 gal is 13x13x4.5 and is just barely ok for our biggest 3.5' RTCs. Just my opinion.