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Having such high cognitive proficiency (WMI and PSI) scores can be quite an advantage, as he would be expected to do well with the kind of output expectations that academically-advanced placements often have of students. This is not always the case for GT students.
His reasoning skills, in contrast, are more in the optimally to moderately GT range, which is still quite strong, but more frequently experienced by schools (one out of about two classrooms, vs one out of one or two schools, or only one in the district). Actually, his profile is in some ways more amenable to curricular adjustment, as it may be easier to convince school personnel of his gifts based on his work products. Not to downplay the frustration you have had up until this point, but this frequency of occurrence does mean that, if your district has any kind of congregated/magnet programs for GT, he is likely to have peers out there, if given access to that program, and he is likely to present in a way that is easily appreciated by the GT teachers.
The trick will be maintaining him until he has access to that kind of programming.
In the primary years, my personal philosophy is to let the child lead. The academic goals of the elementary years, especially the early elementary years, are relatively few, consisting mainly of learning to read fluently, the associated spelling and sentence-level composition skills, and basic arithmetic skills. The first goal is addressed in a reader simply by allowing him to read a great deal, based on interests. The second sometimes comes more slowly, as it is gated by age-appropriate fine-motor skills, but can be supported by allowing children to use technology (typing, speech-to-text, scribing) to free up their language expression inventiveness in written or dictated creative works of personal expression. With his strong memory skills, he may also enjoy memorizing poetry, passages from literature, musical or dramatic works. If he initiates extra math work, there are plenty of resources out there (many here have used and enjoyed Singapore Math, Beast Academy, and others), but generally one prefers that these be child-led afterschooling activities, not parent-directed.
Mostly, I would allow him to play, create, explore, and "waste time" on his own interests. That's really how children at this stage of development learn best.
