There is a basic addition of 1 encumbrance per item on a body part, regardless of what the item's stats are. Hence why you can't wear a few hundred skirts to run super fast.
Incidentally, I've found that the best combination (for me) for a gun-centric character is this setup ([r] is reinforced):
-skirt [r]
-utility vest [r]
-sneakers
-fingerless gloves
-army helmet (if you can get it; otherwise substitute a different helmet)
-backpack (x2)
With that + Packmule, I've got 245 volume capacity, and with decent strength you can get a whole lot of stuff in there. At the moment, I'm a walking armory, with:
-Marlin 39A [silencer] [sniper conversion]
-Remington 870 [double clip]
-Glock 19 [silencer]
-Savage 111F [silencer] [sniper conversion]
-Steyr AUG [silencer] [sniper coversion]
-TDI Vector [silencer]
-Baseball bat
-Katana
-Molotov (x3)
-Ammunition for every weapon, minimum ~40 rounds (Remington, all others are more). I also have a raincoat, several days worth of jerky and water, a few unread books, a spy novel, first aid, a few basic items of equipment, and painkillers.
With all that, I'm overburdened a bit, but this character is fairly old, and has high dodge after spending quite a bit of game time raiding several large towns to find all of that gear. Besides, I'm pretty much untouchable at this point, as my gun skills have gotten high as well. With that Savage, I've got base stats of 54 damage, 105 accuracy, and 23 recoil. Since it is already a 3 round semiauto, all the sniper mod did was up accuracy and damage, and at this point I'm killing pretty much everything without leaving a corpse when I use it. When I run into a horde, I pull out the Vector and singleshot them until reinforcements stop coming. The only thing that makes me a reactive force rather than a proactive one are large numbers of skeletons, and that usually comes down to aggressively wiping out all other enemies before switching to the bat. I haven't had to use my katana more than twice since I found it, and my biggest challenge at this point is making sure I find enough hotplates and salt to keep up my supply of jerky, as I've got a number of glass bottles and a known clean water source.
Plus, double backpacks is much less encumbrance than body armor, trenchcoat, backpack, utility vests combined. I only use kevlar when going into labs, all other times it sits in a safehouse.
With sewing: Yeah, just practice on random t-shirts. If they get reall bad, use scissors and get some free rags.
Regarding experience: I always take the morale-boosting trait (can't remember the name for the life of me) that adds +6 morale permanently. It is cheap in points, and that +6 boost means that every single tick that you aren't being affected by negative things, you have a chance to add to the exp pool, which is very, very good if you spend a lot of time crafting or reading. I typically end up gaining experience faster than I can level my skills, especially once I get a raincoat and start adding booze, mp3 players, and candy to the mix.