You can only have 3 profession levels, so either armorer or small guns to level 3 and level 1 of the other, or both level 2.
As for the character build:
I think ST 7 is overkill for the character you describe, even though you need 7 to get level 3 armorer. You can use buffout to get that.
I'm not sure, but I think uneven PE means you wasting 1 point. I would put it at 6, unless you're planning on becoming a jet addict.
CH can be 4 or even 3 and you're still able to talk to npc traders and do most quests, although some quests will require the use of mentats.
IN 7 could be lowered to 6, unless you want it for the skill points.
1 less ST, 2 less CH and 1 less IN could get you:
1 more PE (or 2 if you'll be a jet addict)
2 more EN for more hit points
1 more AG, but as uneven AG is a waste of a point you would have combine it with the small frames trait. So you could leave the IN at 7 or lower CH by only 1
Mr. Fixit perk isn't available according to the wiki.
If you want to make him a taxi, there are several perks that go well with that like pathfinder and explorer.
Check the wiki for a
list of available perks and their requirements.
