The needle somehow no longer lines up properly... there is nothing wrong with it or the foot area that I can see, it just hits the metal plate when I turn the hand wheel.

SOURCE: The thread is bunching up

Your problem stems from the faulty foot lever mechanism. It's coupled to the upper thread tension control which only provides tension when the presser foot is in the locked down position.

If the presser foot won't positively engage in the down position, there's no upper thread tension and the thread bunches up below. Everything else stems from there. If the needle has hit the bobbin case too frequently then the bobbin timing may also be slightly out and the needle itself will be damaged and won't pass straight through the fabric; it only takes a tiny deflection from the vertical as it passes through the workpiece for the needle to flex and hit the bobbin case.

In summary, your machine is in desperate need of repair and adjustment. You haven't stated which exact Singer model you have, but they are usually easy to get servicing manuals for or you can take the machine to a sewing machine servicing specialist. Most singer spare parts (even for 100 year old machines) are usually still available fairly cheaply from a variety of sources, just enter "Singer spares" into your search engine to find suppliers.

To prevent re-occurrence, clean the mechanism regularly and lubricate it as directed by the manufacturer using sewing machine oil. Depending on how often you use the machine, do (or have done) a more thorough service periodically to check the timing and also that all mechanism screws remain tightly fastened.

I hope that my reply has shed some light on your problem and enables you to decide what to do next. Please take a moment to rate my answer.

SOURCE: My Singer 6160's needle is hitting the bobbin plate.

first change the needle--flat side to the back of the machine, make sure the needle is inserted all the way up into the needle holder
make sure it's the correct needle for the machine
if the needle keeps hitting the bobbin plate then the machine may be out of time & would have to be take to a sewing machine shop for retiming.

SOURCE: Needle hitting metal casing .. Singer Futura CE 200

It happend to me aswell , not getting the source of the problem!
Then I noticed that the bobbin casing was out of the original position, take the whole casing out and make sure that when you put it back that the small metal tension loop at the front side on the right is correct, this image you can see in your handbook, (placement of the bobbin casing)

SOURCE: Hand Wheel Won't Turn

The "Bobbin stopper" is in the incorrect position. It moves from side to side in a switch like motion. In one direction, it locks up the machine. That is, you can turn the wheele backwards, but not forward.. The bobbin stopper can be found in the book that cam with the machine. In our book, it is item #9.

SOURCE: Singer Stylist 834

It needs a good cleaning of lint, thread etc. take your bobbin case out and make sure that there is nothing in there. DO NOT TURN YOUR HAND WHEEL BACKWARDS! It will mess up your timing. If you cannot free it up take it for service