According to Messerschmitt himself in, a reply to Goering on 2nd November 1943, the Me 262 had always been designed with the possibility of fitting bomb racks. This is hardly surprising, given that both the Bf 109 and Bf 110 could be thus equipped and the Me 410 had an internal bomb bay (as a planned version of the Me 262 would have had). Goering asked the question because Hitler had made it clear that he saw a role for the Me 262 as a fast bomber. Maybe he was intentionally sabotaging his own war effort

There is even a picture taken of this happy occasion as Milch, Luchts and Goering met Messerschmitt to review repairs at the Regensburg plant following allied bombing.
On 26th November, during a demonstration of new German aircraft, Messerschmitt told Hitler directly that the Me 262 could carry a 1000Kg bomb load. The idea that this was an effort to sabotage the Nazi war effort (by Messerschmitt, take a look at the company finances) is ridiculous. It was an effort to get his aircraft built and to make money for the company. Business doesn't stop just because there is a war on.
The Me 262 and it's engines had the highest priority ranking available to any weapons programme. This priority category was code named Vulkan. It gave the Me 262 presedence over ALL other RLM/Luftwaffe projects and Milch sought to extend this across the entire armaments industry. On 10th December 1942 Milch, as State Secretary for Aviation and Generalluftzeugmeister issued the following order.
"The absolute demand for qualitative superiority of Luftwaffe equipment, over that of enemy countries, has led me to order the creation of an urgent development and production programme uner the code word Vulkan.
Tasks proceeding under this code word have absolute overriding priority within the Luftwaffe.
The programme includes jet propelled aircraft and guided missiles, including associated equipment and the ground organisation necessary to support these activities.
A request has been made to the Reichminster for Armaments and Munitions to extend the legal force of the code word Vulkan throughout the entire armaments field. Development of some of the following equipment is already taking place under priority DE. Through the code word Vulkan priority will also apply to the procurement of this equipment, for which extensive preparations will have to be made as before."
So Vulkan trumped the previous priority DE, which was already the highest priority production status that could be accorded any programme within the German armaments industry. I don't see how that equates to a failure "to ensure that the Me 262 was given priority over tanks and U-boats from the nickel supply viewpoint", or any other view point.
Programmes covered by Vulkan were: Me 163, Me 262, He 280, Me 328, Ar 234 and the engines, Jumo 004, BMW 003, BMW 018, HeS 001, DB 007, As 014.
The men who compiled that list did not have, as we do, the benefit of hindsight. Suffice to say that both the Me 262 and Jumo 004 had the highest possible priority within the German armaments industry from December 1942.
As for the other points you raised, someone else can answer them!
Cheers
Steve