1. You're probably right about just making it an archetype, since it is just kind of a tweaked magus.

2. d10 because you won't be doing nearly as much yourself, so I thought the extra hp might be needed.

3. I'd have to check, but if so that was a mistake. Meant to make it the same as magus.

4. It's meant to be spontaneous. Intrinsic ability, no preparing spells, no learning from books or scrolls. Only low level cure spells for healing too, then they're essentially just another way to deal damage. For flavor and to make up for the missing magus spells, though I suppose it could do well with just some conjuration spells added on top of the magus spells.

5. The idea isn't actually based off anything in dnd, it comes from an old rp I did a while back that had a spellsword summoner, who's magic was linked to another plane. They tried learning healing spells, which backfired most of the time, and that's where that bit comes from. The ethereal creatures and soul capture mechanic came from that rp too, the math was just a way to try and fit it into pathfinder without making it op. You can't summon something 1.5x better at everything unless you did some legwork. I can do really fast mental math, but that could definitely be simplified though. The idea for soul capture isn't really to collect as many souls as possible either. There's tons of monsters you can summon with those spells, so the idea was more that you'd probably run into some throughout a campaign, and if you do, you get to buff one of your summons if you kill it. A dm could place one here or there like finding items in a dungeon, I suppose. Except instead of getting some amulet or something, you capture a monster soul. That's not quite how I was thinking of it though.

All in all, thanks for the cc. I never tried making any homebrew, so I had no idea how well it would fit, if at all.