So, in regards to strength requirements. A strength of 2 or 3 is pretty damned low - assuming a medium-sized servant that can lift 30 pounds, it's not going to have a whole lot of impact power. Lifting a bucket of water, sure - but throwing it? Harder.
I work as a carpenter. I'm the small guy on the team, but I'm strong enough to get most tasks done. For a while, we worked with a tiny guy who really wasn't cut out for the trade (and he was only there because a government program put him there). This guy could barely lift a few 2x4s, had a hard time swinging a hammer, and struggled to move a wheelbarrow. I'd argue his strength sat around 6 mark, were he a D&D character. So, still stronger than an unseen servant.
Swinging a hammer, sledge hammer, axe - all of those could be done with a 2 strength... but the impact force wouldn't be any better than if the servant DROPPED it. Because all of those tools are strength multipliers... and if your strength is low, they won't be any use.
A neat side note - I'd assume Unseen Servants never get tired. This means that, over an hour, they might actually get repetitive low-strength tasks done quicker than a strong, skilled labourer could... things like pulling nails, using a crowbar, etc, because they never get tired.
Honestly, though, I don't like being this much of a stickler in play. When a player uses Unseen Servant, I tend to ignore their strength score and instead just let things fly based on creativity. In 3E, we had a wild mage who would cast mass unseen servant and equip them all with tools. Pretty soon, the entire isle of dread was criss-crossed with roads that the mage built as they travelled through the jungle.