If I remember correctly he has these three options open to him. Yet I read somewhere about getting 2pp or 1pp and a metamagic. But I don't recall where I read it or if I really read and i'm just making stuff up () But here is what i know for sure he can do:

Raise Magic attribute by 1 + gain a power point + learn a new metamagic technique; or
Raise Magic attribute by 1 + gain a power point + alter astral signature; or
Shed a geas.

Am I missing anything?

There is an odd reading for magician's way adepts that concludes they can increase their power points by 1 and their magical power ability by 1 instead of a metamagic or signature change. Best to just ignore that possibility, and it is completely irrelevent if a normal adept.

Yes, those are the typical options. It gets a little less odd when dealing with magician way types if you clarify that the increased magic attribute is the source of the extra power point which magician adepts can then put into their specialty power to improve their effective magic rating with sorcery and conjuring.

Ok, here's a question: can an adept (plain, ordinary adept), upon initating, gain a new power? Say, Astral Perception, killing hands, etc? Or are you limited to metamagic/signature altering/geas shedding?

Any time an adept's magic rating increases (initiation which does not shed a geas), they gain a power point which they can spend on any power they so choose -- be it a new power or adding levels to an old power. They can also 'save' the power point for future initiations, for instance astral perception, which costs 2 power points (1.5 geased).

There's some debate about whether you have to be taught an adept technique, or whether it just comes naturally. The metamagic does have to be separately learned in any case.

Under Sheding a geas, say i have 1 Geas apply to 3 Magic/Power points worth of powers, do i lose the geas to all of them or just a 1 point's worth?

Only involuntary geasa can be shed, not the voluntary ones that reduce the cost of powers. Each involuntary geas represents a specific circumstance hemming about either one Magic Point/Power Point worth of powers, or a +2 to magic-related TNs (spellcasters/conjurers).

Thus each such condition, per limiting one Magic Point/Power Point or adding +2 to TN, requires a separate "remove geas" to remove.