DD9 and I have a somewhat lower, though similar cognitive profile, and both of us have gone through the same issues in math that you describe. We've both always shown to be advanced for our development stages in procedures and concepts, but prone to bone-headed mistakes, and difficulties in translating English problems to math problems.
The first issue is related to big-picture thinking, and lack of attention to detail. The only solution to that which I'm aware of is a metaphorical rolled-up-newspaper-whack-to-the-head to pay attention next time. The newspaper has taken different forms for DD and I, due to our different personalities. I provided my own, because I wanted to beat everyone in the class, and getting marked down (and therefore not winning) for casual mistakes were the equivalent of kicking the ball into my own goal, and my competitive nature demanded I do better next time. DD needed outside support, because she's liable to think she's losing points because she's not good enough, and make even more mistakes later. In her case, we came up with an external reward system wherein making boneheaded mistakes costs her the chance to earn some money. I can tell how successful it's been because she currently has more discretionary spending money than I do (while being effectively grade-skipped 2 years in math).
As for word problems, my personal definition of math is that it's a foreign language that describes relationships. It's also entirely abstract. So a "mathy" kid is extremely fluent in the language of math and abstract ideas. Word problems expect the student to translate from English (which is a lower skill for your child, as demonstrated by his VCI) to math, and from concrete to abstract, then back again. There is a lot of cognitive heavy-lifting going on in this process, and it plays to our children's weaknesses as well as their strengths. Throw in some math accelerations, and... yikes.
My DD would typically respond to a word problem by seizing the numbers and jumping into operations against them, often without any regard for how they reflect the concrete reality of the story. As much as my DD loves working with me on various subjects, word problems sent her to her room for meltdowns on a regular basis... because in order to get her through this, I used my metaphorical newspaper on her. I couldn't do all the translating for her, or she'd learn nothing, but I did have to keep pushing her to do it on her own.
Like any learned skill, it gets better over time, given enough effort. DD certainly ended this past school year in a better place on word problems than where she started it.
