If you use the same angles of deflection (as in scale the throw measurements along with the model) then the model will fly pretty much the same. In fact you may find you need a little more throw to get to the feeling you want. Small models tend to be quite responsive to control deflections so it's not uncommon to see the larger versions of the same design using more angular throw than the little guys.

There's no ideal amount of throw angle. It's up to how you want the model to respond. A pilot that is in training will benifit from reduced throw while a more skilled pilot will enjoy the snappiness of a greater angle.

Depending on how much you blow up the plan you may need to add in wing ribs to support the covering and wing parts better. Similarly with the fuselage you may need to respace and re-engineer the number of formers. Or at least add stringers to better support the side material from bowing. Where and how is a matter of previous knowledge and judgement. Not much help for a newbie I know but this is why it's best to start with plans in the correct size until you learn what works and why.

If your enlargement will only be up to around 15% larger then you don't need to do much other than maybe perk up the wing spar. Otherwise you're in for some serious re-engineering to make the structure work for you.