Also not an expert on machine repair - but I've been tinkering with my 562 for over 30 years now.
"Good Call Hal on the feed dogs" - and another area I have had trouble with is the Reverse-Stitch Lever.
A great Feature - But if I do not "Lift" the arm up each time after using - my stitch spacing is tighter.
I made sure to inspect/lubricate the internal mechanism and found nothing suspicious - so - I just remember to "Lift the Reverse Handle" - Another area which I play with is the; "Foot-Height-Lift-Adjustment" - When I find my stitches a bit closer than the wheel setting, I raise the foot height adjustment as it was creating drag on the top layer of material. And finally, check your Top Thread and Bobbin Tension Settings - Try going a little looser on the top - and tighten just enough to 'bury" the knot in the middle of your fabric - Good Luck !

In Addition to the great advice from Fred Mattson, I would like to add the following;
As it appears from the photo you supplied, there is an existing landau top on the car. There are pluses and minuses regarding this. On the plus side, there will already be "trim" fastened at the edges and if in good shape, and carefully removed, may be reused after you install the new top.
Yes, use a quality heat-sealed replacement - and only sew if you're looking for a Euro-look with a convertible top material, like "Haartz" .
On the minus side, as you remove the existing top, "there will be some rust in some very critical areas" - like where the top tucks in under the window trim. Use the correct Trim-Bracket-Release-Tool which is available from most body-shop supply houses and carefully remove the windshield trim. You do not want to kink this and if you're having trouble, then please, enlist the services of a quality automotive glass technician . . . it will be a lot cheaper than trying to replace the existing trim molding !
Preparation: This is critical for the replacement top to look original. Aside from the rust you find around the windows, which should professionally repaired, there will be a lot of residual contact adhesive on the roof and sail panels. You have to completely remove this - all of it - otherwise the final result will be lumpy! Depending on the condition of the glue; If dried out, a few passes with a DA sander works well, if the glue is not dry, then the DA will just gum everything up - in these cases, I use a chemical solvent, like "Afta".
Ready to Install -
Dry-Fit the New Top - Fold the Top in half and cut a Center line V-Notch and then place some masking tape on both shields at the centers - Line up the V Notches and do some light trimming of excess materials - Sure - apply the contact adhesive Fred recommends - and be sure to do it evenly.
Let the glue dry to the point of your hands not sticking - This semi-dry condition will allow you to place the freshly glued top on the car and allow you to reposition it - so long as you do not press down firmly.
Line up your center lines - and then press down firmly on the top in the very center.
Now, you can work from the sides and pull out from the center and smooth out the vinyl - from the center out. When working the rear sail panels, you may need to use a heat-gun to soften the material, so you can then stretch the vinyl where the side sail panel meets the rear window area. Yes, a little experience helps here so as to not get wrinkles in the corners.
Take your time, if the glue gets too dry, you can reactivate it with the heat gun.

Hi Tom, In consideration of the actual man-hours for what your are describing, I think there are more solutions to consider than modifying your existing steering wheel. I would recommend looking at vintage wheels from Momo and Nardi - and not touch or modify the original wheel - several models of Alfa's from this period are rising in value - and your original wheel - even with the damage - is more valuable to keep as is.
I have used Momo and Nardi wheels on many vintage Ferrari's/Lambo's/Maserati's which look period correct - and you can order the diameter which chooses your needs.