There is a patch available, which fixes some game imbalances. Do a Google search on Arcanum Patch and follow the links until you find a live one.
1. As mentioned above, the maximum in-game level is 50. (This gives you a maximum of 64 build points, including the five you got when you created the character; you get an extra point every fifth level.) There does exist a 'Level 127' hack, but it's overkill unless you love to Godmode.
2. The basic conceit of the game is that magic works to hinder technology, and vice versa. And on top of that, certain followers don't get along, for alignment reasons: they either talk down to each other, or refuse to join your party if the other is already there.
2a. You have a maximum number of follower slots, based on your Charisma and your mastery of the Persuasion skill. Dog (the 'worthless mutt' that can be found in Ashbury, being kicked to death by its owner) is a free follower, as are any constructs you make or familiars you summon.
3. Spells and basic tech attributes are learned by spending points on them. Higher-level spells require more Willpower, while higher-level tech needs more Intelligence. Tech schematics can also be found in certain shops, in dungeons, and in a side-quest on an island you will visit. Learn them by dragging them into your hotkey bank (the row of boxes below your inventory) and then clicking on them.
3a. There are no spells or tech items available outside of the game, via patches or anything else. Keep in mind that the nature of the game makes it worthwhile to pursue one branch or the other, but not both.
4. To craft an item, you need the supplies (which might in turn need to be made using another tech skill), either the tech skill or schematic the game requires, and sufficient technical expertise in the given skill(s). Technical expertise is acquired in one of two ways: by taking rank in a tech college, or by purchasing tech manuals at a private shop in the University section of Tarant. (Those tech manuals need to be in your inventory when you attempt to craft the item; and they're heavy, so find a place to store them when you're not using them.)
5. Created items last forever; certain magic items have a fixed number of charges, but their base properties work indefinitely regardless.
6. Taking rank in the Repair skill allows you to fix your own stuff; Mastery of Repair allows you to fix it as good as new. (With any skill, you can purchase Apprenticeship if you have at least one point in the skill; Expertise with three points, and Mastery with five points. Also, every skill has a minimum attribute you must raise to add more points; for Repair, it's Intelligence.)
7. As I mentioned above, it does not. It is considered a 'free' follower.
8. All followers act in accordance with their AI, which often means attacking on their own, even if you were preparing to cast an area spell. You have a limited ability to tell them to 'spread out' or 'back off' for example, using the F2 thru F6 keys. You get a portion of your followers XP when they make the kill, but not as much as you would have on your own. (Which is one of the reasons I personally eschew followers in this game.)
9. If you rob or pickpocket someone successfully, the only negative consequence is a small tick toward 'evil' in your alignment. Your alignment affects which quests you're offered, which followers will join you, and the options available near and at the game's end. It allows for more playability; go through once as a good magic user, for example, then the next time as a thief or an evil scientician.
9a. Get into the habit of autosaving (F7) right before you attempt to rob; if you're caught, pressing F8 will restore the game and let you try again. Also be sure to save (using the Save function on the main menu) every time you've completed an important objective or are done for the day; it's important to have a backup save, just in case.
10. Decide what type of character you want to play first, and concentrate your build points there. A crappy fighter-mage-thief-scientist-salesman-blacksmith-etc. does nobody any good, and will quickly get you killed.
Above all, have fun.