Trigger Warning

A peaceful land, a quiet people.

The line before it answer's your question. I don't think 'my' is meant to mean anything more specific than the man he sent in that it was Jaime who sent him.

Sam has no will, anyone given this position would basically be the lord of Horn Hill and just exploit it.

Pre Night's Watch I couldn't see Sam following through with becoming a maester either, it's a life of hard work and dedication. Sam just likes reading, being a maester is more than just reading.

Not at all, the slightest bit of intimidation and his vassals will walk all over him. The stable boys could probably make him do whatever they want.

Although it's entirely possible that the visions showed it accurately I'd still take it with a grain of salt that anything seen in the House of the Undying might not be an accurate look into the past and instead just a representation.

The problem isn't enemy fleets, where's he going to source these supplies? With what money? Through storms when the city is already starving? The logistical nightmare of bringing in supplies by sea on that scale would be an impossibility, no one's going to be swayed to join him when he's trapped in a besieged city with men of dubious loyalty and a populous of starving people that have been ravaged by a sack that outnumber him 30 to 1. Then again Tywin doesn't even have to besiege him, he can just leave him to rot. The only way he's getting food is if he sends his men out to ravage the crownlands and that might not even be sufficient to feed his own men, let alone the entire city. Once those men have plundered King's Landing the prospect of sitting there to starve for Stannis of all people is going to be weighing on their minds heavily. No Tyrells, no food.

This seems like something that would have been so historically iconic that it would have been explicitly mentioned in the text by now.

Tywin could have broken Stannis' army by himself, his vanguard could have probably done it. They were taken completely unawares in the rear whilst they were in the middle of storming a city... across a river... with half their fleet burning. Even a much smaller force would have probably crippled their morale the second they heard fighting behind them, being attacked in the rear is devastating there's a reason most armies withdraw from a siege when a relief force is on the way, the hammer and the anvil is no joke I don't think it would have been a tough fight at all. At the Battle of Barnet the arrival of allies was mistaken as the arrival of enemies at the rear, fighting broke out and confusion spread through the line, the Lancastrian centre began to collapse as fear and confusion spread... now imagine that but with masses of heavy cavalry ploughing into the rear. Honestly their morale should have been crippled the second their fleet turned into a fiery hellscape of death, what nutcases would cross a bridge of mangled ships after all that death to what? Emerge beneath a city wall and all their archers with no siege equipment? Stannis' men are berserkers until they're not.

Personally I've always believed that as you've said Stannis' personal convictions regarding the throne get in the way of his military sensibilities, it's the only rationale I can think of for the Blackwater but all the same I still see the Blackwater as one of the least well set up parts of the series, I feel like GRRM was picturing this cool battle and filling in the plot points to make it a reality rather than building a set of circumstances that led to it more organically but that's just how it came across to me as I read it.

Even if Stannis took the city and the Tyrells didn't move against him his only option militarily would be to break out and withdraw if he couldn't appeal to the Tyrells to join him and relieve the city, he has no supplies in a city of 500,000 starving people. I don't think GRRM really put that much thought into the take King's Landing strategy on Stannis' end it's just setting the stage for this big climactic siege battle that can more or less wipe the slate for the next stage of the story of the War of Five Kings. King's Landing was a poisoned prize without Tyrell support.

Tyrion should have been winning but as GRRM wrote it he wasn't, maybe all of Stannis' men were just terminators with no morale check until their boy Renly turned up again. Blackwater's a big dumb spectacle battle but it's fun to read and that's what matters.

Marry Roslin and provide to some extent for any potential child that Jeyne may produce, he's a king and he needs to put his kingdom first.

Pure temptation right here.

Hey now I thought you wanted Slynt to follow orders.