I might as well buy a new td-w8970 v1.... But man this router thought me so much 
I think something related to network in general is broken especially related to Wi-Fi, probably hardware and specific to my router BUUUUT I have to say that, doing these thing got me less crashes:
- Wi-Fi disabled if I'm home alone (this helped soooo much)
- trying these experimental drivers helped a lot
- separating ethernet and Wi-Fi on two networks (192.168.1.X and 192.168.2.X), disabling the bridge
- disabling VLAN
- connecting only my PC (ethernet) and nothing else (this helped the most combined with no Wi-Fi, but of course the device is much more useless in this configuration)
When I do everything described there I can almost reach 6h of uptime, which is a record but, still not enough.