If you want to play at higher resolutions or need widescreen support, then get the download version. If not there isn't huge difference between the disk and download versions, but either way it is up to you.
I don't know if the Freeze skill on a weapon still ignores the target's resistances in the download version (it wasn't mentioned in the change log). My first game I only noticed that bonus a couple times, so avoiding it (after trying it briefly) didn't put any significant restrictions on my selection of weapons.
You are correct about the Sword Expertise and Assassin's Kiss skills. Even with Assassin's Kiss maxed, you would do more damage with a decent sword.
Unlike with swords, there are only a couple potentially good quality daggers consistently in the game. If you want to play a thief/assassin type build you can certainly do so, though.
There are 2 handed swords. You can get a two handed bastard sword from a knight in an encounter near Stormfist castle, with the right dialog options. Earlier merchants may not have 2 handed swords, but later ones will (and they should start showing up in random loot or dropped by opponents).
If you head east of the farmlands and the castle, you will reach Ars Magicana, a market square with wealthier merchants.
You can trade crappy loot for potions, etc, and better quality loot for more expensive items. In the trade window, click on any items you wish to sell/trade, click on any of the merchant's items you want to buy, then click on the balance icon for whichever side is less, to make up the difference in gold (if available). I almost always used loot when trading, and kept chests in my base with crappy loot, equipment that needed to be repaired, and full durability equipment ready to be sold (repairing an item with less than full durability increases its value).
New Money Trick found - once you explore the dwarven halls in the Dark Forest
You can give merchants stuff to increase their opinion of you, but the merchants you trade with frequently are going to get to 100 in any case, so there is not much point in doing so.
differences between classes (minor spoilers)
Early Starter Tips (NON-Spoiler Version) (contains much of the information in the above topic)
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