I'm working my way through SoA, and I'm almost to Spellhold. I was just wondering what lvl the new techs come in for my char. one like whirlwind and such. Also, with swords/bracers/such do I need to keep for the forge in ToB?

You start getting the high level abilities when the characters in your group reach 3 million experience points. If you have multiclass or dual class characters, add up all the experience for all the classes the character has. If it's 3 million or more (for the same character), they will get a new ability each time they level up, starting at 3 million points. Some high level abilities can't be selected straight away, such as Greater Whirlwind, you have to pick a lower version of that ability (Whirlwind) before you can pick it's stronger version (Greater Whirlwind) at the next level up.

There is one item you find in SoA that can be upgraded in ToB, the Flail of Ages (found in Nalia's Keep). Every other upgradable item in Throne of Bhaal is found in the Throne of Bhaal areas. If you have ToB installed already, the area called Watchers Keep is actually part of ToB, but you can explore it in SoA. If you start exploring Watchers Keep during SoA, there are several items from there which can only be upgraded after you finish SoA and start ToB. Keep all the weapons you find in Watchers Keep and make sure your group is carrying them when you finish SoA. Once you finish SoA, you can't go back to your stronghold to pick stuff up that you stored there. Also hang onto high value gems like rogue stones, kings tears and sapphires. Some items use these gems for their upgrades (although you'll find more of these gems in ToB).

As a friendly word of advice, I would do at least the first level of Watcher's Keep before finishing SoA and moving onto ToB. That first level includes an arrow container and a potions container, both of which act like the gem bag and scroll container you already have: they can hold a great many items. They make it much easier to grab and carry a lot of what you have sitting around in SoA before you make the jump into ToB, which doesn't let you go back.

Note, you don't have to play through all that first level, either. As I recall (it's been a while), at least one of the containers is for sale from the group hanging around the entrance of WK. And I know that there's a good ranged weapon close relatively close to the entrance in WK. It's not a newbie area by any means, but once you progress beyond Spellhold and the Underdark, your party isn't a newbie one, either.

It's worth clearing out the entire 1st level of watchers keep before you finish SoA. I won't spoil it too much, but there are several very nice items you can pick up on that level, or buy from the guards on the roof of watchers keep (they have the potion holding bag and a very nice crossbow for sale), plus some potions of extra healing (very handy to have during the last couple of fights to at the end of the SoA storyline).

Also, when you finish SoA and start ToB, you can't go back to your stronghold. If you've been collecting items that you want to hang onto and storing them in your stronghold, once you've cleared the first level of watchers keep, move the items you want to hang onto from your stronghold to a safe place in watchers keep and you'll be able to get to them in ToB. Sell anything you don't need any more and use the money to buy better stuff (armour/potions/weapons/items) you can use.

First level of watchers keep isn't very hard indeed. Oh, I still need to make a dart using character to use that dart +3.

That's only true for Multiclassed characters. If you're a Dual-class, you have to be 3,000,000 or higher in your ACTIVE class. Also, you're limited to the High-Level-Ability pool of the active class only. For instance, if you take a Fighter and go to Level 20 (I think that's the level you hit with 3 million points) and then Dual to Thief, you will get to choose only one HLA, and you will have to earn another 3 million as a Thief before you can start collecting HLAs again, and even then you can only choose HLAs open to the Thief class, you'll never see the Fighter HLA pool again.