Anyway, the basics you should start with when it comes to solo play is to get Rage and Life Strike, followed by Quick Thinking. Obviously, you have Flow or Primed Flow already. This essentially gets you started on the fact the tanking abilities that matter are ones that outright ignore damage, whether through direct unbreakable face-tanking like Wukong or Valkyr, or through indirect means like crowd control like spamming Radial Blind with Excalibur or World On Fire with Ember. Fun fact in this regard is that the real benefits of Rhino are in the latter category in solo play, since its most potent abilities are the squad-wide deeps booster Roar and Stomp which with proper mods becomes ZA WARUDO. Rhino's true power is causing massive long stuns in a vast area (Power Range modding causes the greatest high), not having a buffer shield.
The base survivability that comes from Rage + Life Strike + Quick Thinking + Flow is pretty uniform and has mild variety per frame depending on health, shields, and armor. The gist of this is that unranked Life Strike allows you to self-heal rapidly with modest energy cost (though it obviously favours melee fanatics like me), while Rage converts damage to additional free energy to save up on pies and being caught with your pants down, and Quick Thinking gives you a strong buffer against death.
On the subject of Inaros, it's a fun and very good frame, and can take a hell of a beating, but it has its own achilles' heels too. While Inaros has enormous armor and health, meaning it can facetank through its durability alone to an extent that is unmatched, it is also the only frame that has no shields at all, which makes it also the only frame vulnerable to chip damage.
If you haven't found a good alternative yet, you can try Loki or the slightly better Loki Prime. T4 Survival void for hours depending on whether you're bored or not without getting hit.
I last played back in U13 up till U14 (kubrows + archwing IIRC), so I don't know if he's still relevant. Breezed through endgame content with a red crit 4-forma Amprex which was better than Boltor Prime back then.
Well, primary change since then is that T4 Survival is no longer the height of endgame (in fact, the old Void system is completely gone), the real test for solo play ability is being able to handle Sorties by yourself. In this regard, Loki's not quite in a position to just and try permastealthing all the way through, particularly if you get something like a Sortie boss mission since Sortie version of Ruk for example hits like a mack truck and needs more bullets to kill than were fired in Stalingrad and IIRC bosses are unaffected by invisibility. Alternatively you get Sortie Kela De Thaym, which also needs a small country's military budget to kill, but also involves dealing with shotgun mines and homing missiles to the face and orbital bombardment when you need to be able to stand still and shoot at a trigger target.
Then again, Sortie bosses are fully a team effort, since if you aren't packing full Corrosive Projection your damage is going to be reduced to such a degree that soloing is not recommended if it's not Krel or you don't get sexually aroused by enormous hp bloat.
Come to think of it, did enemies have the ability to shoot at the player through sound detection back then?
