Why not just use something like matrix/riot.im and host your own sever? Building the app on your own might provide some mental peace, but I don't see what it really contributes other than just reinventing the messenger wheel.

What surprises me most is that the developer is state employed. usually development are performed by software shops or consulting companies, with contracts ending up in hundreds of millions and having sub par quality.

That's a really good sign this might go somewhere this time.

Can anyone explain what are the major differences between Tox P2P messenger and Matrix/Riots? what are pros and cons?

xmpp/irc + otr.

how about instead of spending taxpayer money reinventing the wheel you just train gov. employees to be tech literate?