Creating "Axiom Verge" like shooting mechanic from SPE base

EDIT: Whoops, just realized I can't post URLs yet. The "generic megaman engine" is on this very forum, and Axiom Verge gameplay can be found pretty easily on YouTube.

For those that don't know of Axiom Verge, it's really not all that different from classic Metroid.

My game is an action platformer, and I've been trying to use SPE (Super Platformer Engine) as a general basis, since the actual movement there is very close to what I want. However, I'm also just plain terrible at "programming" (I don't know a lick of any real coding -- my experience revolves much more around the art/story side of things), so the templates help a lot. I've been consuming as many tutorials as possible but somehow I seem to have missed how to implement this system.

It seems like trying to use the "bow" system in SPE might not be the best idea as a foundation, since it's pretty different from what I'm seeking (you can't really move and shoot with it). I've also used a pseudo-Megaman template, which might be better to start with.

Here's the link to that for anyone interested: I've also just tried going from scratch -- certainly the best way since I need to learn how to do these things on my own -- but I'm just really clueless and don't even know where to go beyond getting a simple horizontal bullet going left or right.

Just to outline exactly what I'm looking for:

1. Shooting in eight directions -- left and right, up and down (the latter only being while mid-air preferably, but I can figure that specification out myself), and then the four "diagonal" directions.

2. Running/jumping while shooting, and being able to shoot opposite to the direction you are moving.

Bonus, pie-in-the-sky request:

3. Holding a button to remain stationary while shooting.

I'll post a link to some Axiom Verge gameplay just in-case I'm not explaining myself clearly: ...but again it's pretty much just old fashion Metroid -- not sure about the "hold button to remain stationary" feature, been a long time since I played them. But I'd be more than happy just getting those basic shooting mechanics ironed down.

Any advice whatsoever is most welcome!

Shooting all directions shouldn't be hard, would the player use keyboard or mouse?

I'm actually designing with a controller, but it would be keyboard otherwise. I don't want the total free-aim of a mouse, as seen in the top-down templates in Construct 2 for example.

I'm not sure I understand the question, because you can just set the angle of motion of the bullets..

Hah, actually I think you understand the question better than I do. That was all I needed to know. Like I said, I'm very dumb when it comes to the programming side of stuff, even simple things trip me up (I also suspect that I tend to OVER think certain situations, expecting it to be more difficult than it actually is to implement something).

Thank you kindly!

ETA:

Oh, and any ideas on the "hold a button to stop moving but still shoot" thing? I know it can't be hard, and I think I know what I need to do (essentially, add an event in which a particular button disables movement...which I can do, but it also disables "aiming" since both are controlled with the left stick and/or WASD/arrow keys).