1. Will a regular hole punch (for paper) punch holes in aluminum from the side of a beverage can?
Yes, easily. They don't make packaging like they used to.
2. Can hydrogenated lard be used to make soap?
The internet says yes. I did actually try this five years ago, but must have used a little too much lard as the soap came out with a lardy smell, and yellowed a lot over time. We have been using it as hand soap all this time, and are now down to the last few bars.
3. Can I put a few stitches through my wool-blanket-inside-a-duvet-cover-throw, to keep the blanket from bunching up in the end of the cover?
No, the duvet cover material is not strong enough to hold the blanket if only a few stitches are used. Especially if the children use the throw for playing tug of war. You'd have to use a lot of stitches, and by then it would be a quilt.
4. Should I put all my sweaters on one shelf, and all my shirts (jersey) on another, instead of having one shelf for casual and one for more dressed-up?
Yes, get the sweaters out of the way.
5. Why isn't the upper thread on my sewing machine catching the lower thread??
The needle is in backwards.
6. Will putting extra snaps on the seat covers I made for the dining room chairs help keep them from being pulled off all the time?
Yes, somewhat. The engineering problem here is that if the connection is stronger than the fabric, the fabric will rip under force. (Reinforcing the fabric at the stress points would be awkward.) If the connection is too weak, the covers will be coming off all the time. This is an extremely important point in design, worthy of a block quote in bold:
You have to design not just how it is going to work, but how it is going to break.
Make it break somewhere that is easy to fix.