How to lookup and return multiple values

Before going down the route of expensive array formulae -- have you considered using a Pivot Table with row B as a Page Field ?

If you won't use a PT (and you should have a good reason for not doing so ;-)) then I would advise given the vastness of your source range that you create a concatenation key on source sheet that will allow you to dispense with need for array... eg

Source Sheet ! G3: =$B3&"#"&COUNTIF($B$1:$B3,$B3)
copied down

You can then just use a standard INDEX/MATCH in your table looking first for

34103#1

then next row looks for

34103#2

etc etc...

This will be a far quicker approach to arrays.

But to reiterate - Pivot Table quicker still and requires no additional cells / formulae.