Reading and writing issues

Reading:

My son is a precocious reader. He figured out how to sight-read on his own around his 3rd birthday (he'll be 5 in two weeks), and now he's reading short chapter books ("Nate the Great", those "'DIsney Storybook collections", etc.) I've always thought it's a good thing that he loves reading so much, but lately I've noticed a bad habit he's picked up that might cause him problems later on.

He still primarily sight-reads. He doesn't use phonics at all to figure out new words. If he comes across an unfamiliar word, he'll either skip over it, replace it with another word that "fits", or reads it as whatever he thinks the word is without really trying to sound it out. For example, his newest book contained the phrase "Congressional Medal of Honor", which he read as "Congratulations Medal of Honor". "Kryptonite", he read as "ky-rip-TOE-knee". "Commissioner Gordon" became "Commander Gordon". This wouldn't be a problem if he let me correct him, but he doesn't. If I tell him "It's pronounced 'krip-toe-nite' he'll get upset and say "No, it's 'ky-rip-TOE-knee'!", then continue reading. I even stopped him and pointed out that "Commisioner" has no "D" sound in it. He looked at it, tried to parse the word, and then decided that it was still "Commander".

He does try to sound out words when he's trying to spell them. Vowel sounds give him trouble, but that's normal for his age ('Star Wars' = 'Stor Wors'). But when it comes to reading, it's either sight-reading or nothing. I'm not sure how his vocabulary increases, unless he's figuring out new words from context and looking at pictures, or picking them up when we read to him. Since he's gotten better at reading, he doesn't really enjoy being read to any more, which is when I started noticing the phonics problem. Is this something that will fix itself with time, or once he gets to first grade and is taught how to read in a more formalized way?

Writing:

His reading is well above age level, but he struggles a LOT with writing. His letters are really unformed, and nearly unrecognizable. I don't expect him to have perfect handwriting at this early age, but he can barely make a straight line. We've tried all different writing implements (crayons, markers, fat pens, skinny pens, chalk), and he's equally uncomfortable with all of them. His preschool teacher makes him trace letters on a dry-erase board, and even with the letter as a guide he has trouble. He had to write his name on 18 valentines, and the end result looks like a bunch of random squiggles, one of which *might* be an "E" if you tilt your head. It's obviously not a question of him not knowing his letters (since he knows how to read and tries to spell). He just can't make recognizable letters.  We had him evaluated for fine motor skill issues last year, and they said he was "average", but I don't think it's necessarily a fine motor issue (he does fine with his Legos, and some of those pieces are TINY). I wouldn't worry so much if there wasn't such a HUGE gap between his reading and writing skills. His personality comes into play here as well -- he's not the type to "try, try again" if he doesn't get it the first time. If he isn't able to write something, he'll just abandon it and move on to something he CAN do (like reading). I'm afraid that the reading-writing gap will keep growing and eventually start to hold him back in school.

Again, is this something that they will address in Kindergarten/first grade when they start to focus more on writing skills, or should we be trying something now?

TL;DR almost 5-yo. preschooler is reading above age level but won't sound out difficult words, has terrible writing mechanics. Can we wait for Kindergarten/1st grade and let his teachers straighten out these issues?