Yes, you're incorrect. You can send a maximum of 50 Tech per Aid slot, and so sending 50 Tech and then 10 Tech is inefficient to the Tech Buyer. So is 30 Tech and 30 Tech, and/or any other combination.
Either opt for $3M/50T rates, or go for the standard $3M/100T rate.
In all fairness, you probably spend as much on military attacking these three nations, as you receive from them via attacks (when you consider all variables). They don't have any loot to take, and one of them you cannot loot from as they've not collected taxes in over 13 days. It is general legislation not to aid nations at war, and the larger you get from a profit from any Tech Deals, the harder it shall be to continue this routine of attacking nations -- they'll have to get larger and more likely to hit you back.
Lord, there is a load of stuff, so just consider the fact no-one will Tech Deal with you given your circumstances! Hence, the fact no-one has!
All the best!