Seeking guidance on replacing old tub spout

P.S. New updates and follow-up questions in the bottom. Thank you guys!

this is my first post here and if there is anything against our community rules, please let me know and I would update it.

My goal is to seek your inputs or guidance on how to replace my old bathtub spouts. The spout should be super old with brand names Dialcet Moen on the diverter control panel and Pat No. /newline 1809567 /newline 2022875 on its spout. I would explain my current situation first and then my plan.

I bought my first old house a few years ago and the cost of living has been rising crazily recently. I decided to do some home improvement work myself. Replacing bathroom spouts, diverters, and shower heads is supposed to be one of them. For myself, I have been maintaining my car regularly (for example, valve gasket replacement for BMW E90s) and would consider myself a relatively experienced DIYer. However, I ran into some issue when I tried to remove my current old bathtub spouts.
Here is the timeline regarding what I've done so far:

1. I made some quick youtube search and got a rough idea of what I was supposed to do. Generally speaking, you are supposed to first identify whether your spout is threaded or slip-fit. Then you could either thread it out or unscrew accordingly. I checked my spouts and confirmed there is no screw on the surface of my spout. This suggests my spout should be threaded, which turns out to be not 100% accurate.
2. I sprayed some WD40 and then tried to rotate my spout with pliers. Nothing happened. Too tight. Alright. I thought about it and grabbed my hair dryer. Heated it for a few minutes till it was hot. Tried again and nothing happened. I was a little bored and applied more force. It was moved a little by roughly 10 degrees. However, it is still very tight.
3. Lastly, I cut the front part of the spout with my saw. This exposes the inner cross-section to me and it doesn't help much(you can check how I cut it in the attached images in the end). I then had a feeling that instead of unscrewing the spout, it is highly possible that I twisted my shower pipe inside the wall. This can be implied for a couple of reasons:
   • The spout isn't in a position that fits a regular angle.
   • Seeing from the very narrow gap between the spout and the wall, I notice that the pipe corroded very badly.
   • The spout is still super tight even if it was moved by 10%. If it is not the pipe got twisted, the spout is supposed to be unscrewed easily.

After realizing I might mess it up by twisting the shower pipe inside the wall. I stopped all my attempts and started researching. Here is my major finding:

• My spout is really old. It has Moen patent number on it. Link to us patent (note the patent number isn't exactly the same as that in my spout but they are of the same series and look very similar). Here is an image from the patent page showing the parts.

I now face a big problem and would very much like to resolve it myself if possible. Hiring a plumber would probably cost $2,000 to $3,000 in the current market. Here is my plan and I am desperate for you guys' guidance:

1. Step 1. Use my saw to cut more parts of the spout. This is going to be roughly around vertical line 2 in this image.
2. Step 2. Try to remove remaining parts of the spout by pliers or any tools.
3. Step 3. Hammer my bathroom tiles around the shower pipe inside the spout.
4. Step 4. Replace the shower pipe.
5. Step 5. Retile.
6. Step 6. Install new spouts.
   Does that seem to be a feasible plan? When I replace the shower pipe, do you guys recommend copper, PVC or what type? I am totally newbie in plumbing. Thanks.
   Here are all images I took for a better understanding of the current spouts:
   Image folder in Imgur.

2021/11/23 UPDATE- new pictures after taking off the spout brutally: folder.

I managed to remove the tub spout but not in the perfect way. Eventually, I took too tiles off and used penetrating oil to take down the copper connecter + iron catridge + spout.

Here is what was going on: there is surely a copper shower pipe that direct waters from diverter to the tub spout. The copper shower pipe is connected to a 90-degree copper converter with some silver sealant(not thread for sure because I twisted it downward to remove the spout+connector). The other side of the copper converter is threaded with an iron bar, and the iron bar is then connected to my tub spout, which is a super old Dialcet Moen one.

For more clear illustration, see the new pictures I took in the new folder.

Now the remaining question is, what am I supposed to do next?
Here is my plan:

1. Buy a new copper connector and connect it to the shower pipe.
2. Buy a new copper catridge similar to the corroded iron one and insert one side to the 90 degree copper connector.
3. From the other side of the new copper catridge, buy a new spout and connect them.
4. Seal the wall but how? LOL

I do have a few questions if anybody could provide some inputs:

1. What kind of spout do you recommend in my situation?
2. What would you recommend to put back the tiles? When I take them off, I had to take off some part of the drywall. So I am clueless regarding putting back the tiles.

Thank you again!

My location is in greater Seattle area.
Mike