I've managed to reach the 500,000xp cap with a 6-man party by playing completionist BG1 and SoD, so for a solo player... yeah, I think you'd have enough to get 3 million exp since there aren't many quest experience rewards until BG2. However, the Tweaks xp cap remover doesn't seem to work for SoD.
There are no HLAs in SoD because there is no menu for it. In fact, I think hitting HLA levels will cause you to become stuck on the level up screen.
There is no real need for HLAs in SoD if you are not doing anything higher than Core Rules for solo runs. Basically, I think movement speed to "run like hell" and freedom of action is far more important.
Comments
There are no HLAs in SoD because there is no menu for it. In fact, I think hitting HLA levels will cause you to become stuck on the level up screen.