Constabulary

looks like a clone of the Singer 45K21, drop feed with roller foot.

I´d choose the BROTHER - clone of a Singer 153w (but with reverse) or the later Seiko CW-8 and / or Consew 227R. Its a Singer based machine and parts will be available probably for ever and the accessories like presser feet sets are cheap.

Is it a synchronized binder machine? If yes you may need a fixed (not moving) arm plate. Most likely you will have to modify the hemming attachment and maybe plate to make it work. Please post pictures.

If it was me I would use heavy Denim or Canvas with some leather application (for pockets and straps).

if it has to be a left stand machine look for Pfaff 24 or 27, Adler 49 . alternatively Singer 17, Pfaff 28, Adler 48 (all right stand)

I only see one picture and that looks good to me except that you have not insert a needle . Sewing machines sew better with needles **kidding**. Have you checked the manual? Thats usually the 1st thing I would do.

I have seen Frobanas in slightly different color shades. Maybe that is because of their age or if they were exposed to different "environments". The latest I have seen where hammer tone silver.

are both of them piping feet and are they for the same piping thickness? I think feet for thicker pipings are probably shorter but it´s a guess.

If your motor is an old clutch motor you will not have much fun with it (often too fast and noisy). Better replace it with a modern servo motor and maybe add a speed reducer. Or check this thread maybe this motor is a good option for you

Unfortunately Pfaff has no "counterpart" and you have to use their gauge parts. When you want to change the needle distance you need a complete gauge set that includes presser foot, fed dog, needle plate and needle holder. Pfaff gauge sets are hard to find and even when you find them they will be quite expensive. When it comes to double needle machines I´d recommend a machine that is based on a Singer machines, like Juki, Seiko, Consew and so forth. Singer based gauge parts are available everywhere and they are cheap. Check the list of manufacturers in the description here: https://www.ebay.de/itm/142635430976

I would check for SUTTON or McKay stitchers, IIRC Pederson models are sometimes very similar if not identical. Just what I have observed from the shoe making guys. Maybe even BUSM / British United Shoe Machinery, MOENUS, ALBEKO or PROTOS.

Is it just test sewing what we see or is it a piece of a product you are sewing? Why should a post bed machine with a single row feed dog and a roller foot sew a fairly large piece of material straight when not guiding the material with your hands? What product do you want to produce? Maybe wrong machine for the job? You do not give us many information...

G is made in Germany W is made in USA otherwise the same machine (depending on sub class) and interchangeable parts.

when I have learned something in "my sewing machine years" then it is never take it apart fully when it is not absolutely necessary even when you think you know a lot about sewing machines. Obsolete parts can break in worst case. Even on "simple" machines like patchers things can go wrong when you strip it fully and you are f...ed when you but back the cams the wrong way.... You name it. Just don't do it for just for learning or cleaning. I know this does not help - just my statement. Hard to tell what you did wrong w/o having followed the process. Maybe a short video would help.

I´d rather check with the manufacturer

it probably depends on the subclass of the 1245 machine whether it has an oil reservoir or not. I can Speak for the Singer 211 series and they came with different size hooks and some of the hooks had oil bath others don´t depending on what subclass the machine has.

Have you googled the number? First find was in AU https://marfar.com.au/pa/collections/parts/products/spring-412201 I know AU - Denmark but still an option. Alternatively I would check parts lists of similar machines like Seiko LSW, Brother LS2 or similar, also look for similar Consew models. Just a guess, I don´t know if they are all the same underneath the flat bed. If you find nothing, check with some of the known Chinese sewing machine parts dealer on Ebay and ask if they can get you the spring. I did that before and they came up with what I needed. That probably is the cheapest option. Just some suggestions.

BTW - seems your machine has no oil drip pan.

tilt the machine back its just below the flat bed right in front of you.

Please post more pictures of your machine. Its hard to imagine what you mean. Pictures tell more than 1000 words.

aaaah, well - its for adjusting the foot pressure

needle not correctly insert, worn hook tip, needle - hook timing needs to be checked & adjusted (see manual), hook tip too far away from needle... there could be many reasons.

I bought from then directly too but that was some years ago. Nice people. I visited their factory back then and they even showed me around. Most impressive was the Zick Zack patcher they sell. But expect that made in Germany parts and especially hooks are quite expensive - guess how I know. The spare parts folks said (back then) that certain parts (like hooks) may work for the old machines but may need some slight altering. But better check with them, things sometimes change...

looks lie a Singer 95 or 95K clone it for sure can sew some garment leather but it is designed as a tailoring machine. So depends of what you want to sew / produce if this machine is suitable or not.

when i start sewing I have top and bottom thread UNDER the foot.