You'll be fine. If you find a sword or spear that drains life, give it to him so he can keep his own hp topped off. He'll deal melee damage for you, and he provides an excellent pool of hp for the others to use with Shared Life to keep everyone healthy. If he goes Insane, you don't need to cure it (the stats that are lowered don't matter to him, iirc).

Also, make sure he takes care of all of your miscellaneous skills, like Disarm Trap and Merchant. Letting the Knight handle all the "one character per party" skills for the party lets your casters focus their skill points on magic skills.

I know I'm in the minority here, but I preferred might rather than magic in my MM6-8 games. By the end of the game, the only thing I really wanted from my casters were the buffs and utility (town portal, fly), and healing, though they did cast the odd offensive spell, especially the ICBM ones outdoors.

You should be completely fine. Your buffed up knight will be very useful throughout the game.

Thanks! I'm having so much fun with the game. Yah my knight is tearing through baddies and with all your feedback I'm happy to have him lol.

He does have magic. That is what wands and scrolls are for.

Wands will have the number of "charges" listed. As you get close to 1 or 2, you can recharge. These recharges are of a diminishing return and the Wand will fail eventually. If you try to "load up" the wand when it has over five charges left, you can lose Charges. Three types of recharges: scroll, potion or spell (if no Magic Caster, the third isn't available.) .

In MMVII, there are wands that have no charge and can only be sold. But I don't think this is a problem in VI.

Not in MM VI. But shopkeepers pay just as much for wands down to the last charge as they do for fully-charged ones. (One of the tutorial-type NPC remarks confirms this.)
Not a problem for randomly-found wands, but is for two hard-coded ones that I know of. One dropped by a boss monster and the other found in a secret treasure location.

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By the way, fly scrolls and water-walk scrolls may not work for knights. Because once the spell is cast, more spell points are taken from the caster, something like one a minute or so, whenever actually air-borne or water-borne. So if the caster has no spell points then the party cannot take off.

Fly burns about 1 per 5 minutes, while Water Walk is about 1 per 10 minutes, and the spell is cancelled when the caster runs out of spell points, so a Knight cannot effectively use a scroll of either one. Also, a Knight can't very effectively use a scroll of Lloyd's Beacon, since it checks the user's skill in Water Magic for the duration (setting aside that you'd need two such scrolls for the spell to be useful to a Knight at all).

A Knight can use wands and potions just fine (which aren't tied to the character's skills), but I wouldn't have him use any scrolls unless he is curing a status effect when a caster isn't available to do so.

That water walk comments explains why I have had problems now and again.