Should I Replace ATmega328P????

but have been a bit frightened to tackle SMD stuff yet.

Try removing stuff first, and using a scrap board.

Blowing the parts away so they float along on a sea of solder

Yes that can happen but it is no problem because the solder does not stick to much being a thin film. Get a good pair of tweezers.

Everything not quite lined up properly

Yes that is the biggest problem.

Solder bridges

Use the minimum amount of solder, you also find out the value of a good solder mask.