Thanks so much for being willing to share a little more about your son. That does help!

From what you've shared, it doesn't sound like his eyesight is a problem, since he reads chapter books well. It does sound like you've covered your first big chunk of necessary phonics with "Teach Your Child To Read in 100 Easy Lessons" and that your little guy prefers to read whole to part rather than part to whole. Some kiddos just do!

It also sounds like fine motor wise, he's doing alright, if he builds easily with small Legos. I wouldn't worry much about the drawing, some kiddos don't have a bent for that, and it takes much practice and time to learn the drawing skills. And it can come much later in boys requiring specific tips and suggestions on "how to draw". We've had goals at the pediatrician we haven't met "on time" either, and I thought some of them were very difficult. Yet, my kiddos are coming along just fine!
It does sound like your son is having trouble visualizing the words in his mind, which is the most common problem with kiddos (and adults) who struggle as spellers. So, the lessons in "Beyond..." along with copywork should be helpful. I would make sure to do those two things at least 4 days a week to strengthen the muscles needed for writing and to strengthen the ability to visualize words in his head.
I would possibly consider adding "Phonics Pathways" for spelling help as well. I saw Melanie mentioned it too, so I'm sure she can share more about it. It is worth checking into to see if it might also help fit your son's needs.
One additional strategy that is easy to use when beginning to spell basic words is called "stretch" and "shrink". You stretch the sounds in the word apart (while the child is holding and stretching a rubber band) and then quickly shrink the sounds back together (while shrinking the rubber band back together). So, the child would say slowly say c...a....t.... and then cat. It helps them hear each individual sound before spelling it (or reading it for that matter). It helps those little ones who don't like to "take a word apart" see the parts and then shrink them back together to make one word.

We're glad to have you here! It sounds like your little guy is doing great and just happens to have spelling as his tough subject. All little people have areas of strength and weakness. Spelling is a very common area of weakness!

Blessings,
Carrie