Problems backing up iPhone 8 and syncing with iCloud

I am after help with backing up my iphone 8 plus & iCloud photos. I have been struggling with this for a week.

I’ve always had iPhones & only ever backed up my devices to iTunes & Pc. Now my pc is old, running very slow & doesn’t seem to be coping with attempting to backup my phone. Even though I was under the impression I had backed up several times in the past 9mnths the last backup showing in iTunes says it was in mid 2018!

This means I do not have a backup of my dataA & as I am looking at getting a new iPhone in the next 2 weeks it’s becoming critical that I have one to set up a new phone from.

I am:

Running Windows 7 on my pc

Running 11.2.2 ios on my iPhone 8 Plus (I want to update it but not until I can get a current backup)

I Have 15,500 Photos & 280 videos that are very important to me that I do not want to lose.

I am looking to borrow a pc in the next few days that is running a current software & will be faster however I'm not 100% confident its going to solve my problems or that the backup stopping partway will cease.

I have been having the following problems:

iPhone started playing up at the charging port. It would be connected to power/USB port & just disconnect itself after a minute or 2. It would intermittently charge & I've had varying suggestions on the problem from they cant see anything wrong in the port, to something looks broken down there, to it looks perfect in there, however some chips in the iphone 7 & 8 can fry & even with a new charging port it wouldn't fix the problem & I may need a new chip.

iPhone will not back up to the pc via a cable (maybe because of the charging port issue?) The back up starts & gets about 1cm along the progress bar & then disconnects and says “iPhone cannot be synced because the connection to the iPhone was reset. I have tried all the suggestions online I could find in regards to fixing this problem like resetting the network settings & resetting sync history but they did not rectify the problem. I have also renamed the backup folder in windows to backup1 trying to encourage it to think it had never backedup & to created a new one from scratch but it didn't help.

I have tried syncing the iPhone to iTunes over wifi but the same thing happens, I get about 1cm along the progress bar (& it struggles for ages, running slow, spinning wheel starting & stopping) then get the “iPhone cannot be synced because the connection to the iPhone was reset” error. I'm not sure how much my old & slow computer is playing part in this.

The iPhone is not recognised when plugged into some CD players via USB cable.

The iPhone intermittently is recognised when plugged into the computer but can disconnect itself after a couple of minutes or if the cable moves may disconnect. I have managed to manually extract my photos/videos to an external hard drive in between the intermittent disconnects but would still like a proper and full back up of this iPhone.

I have been charging the phone via wireless

I have purchased 200GB of allowance to sync my photos & video to iCloud however I am having the following problems:

iPhone is telling me there is 53GB of photos on my device

It has only synced 6500 photos to iCloud, or 22GB

The backup graph on the storage bar originally showed 60gb of backup after the first backup. Now after other backup attempts 50GB has disappeared & now it shows 9GB. I’d have thought for a 256GB phone that’s nearly full I’d have had more backup than that?

I’ve logged out, turned backup off, iCloud Photo Library Off, reset the phone, turned iCloud Photo Library back on, turned backup back on & I still can’t get the rest of the photos to sync. I've tried toggling everything on & off that I can and reset the phone many times.

When I select "backup now", the progress bar starts off with estimated time remaining and varys in the amount of time, but goes as high as 45 minutes (which sounds good!) then within seconds as it progresses it goes to for example: 38 minutes, 7 minutes, 4 minutes & then just seems to cancel itself & goes back to the backup screen with "back up now" & says "last successful backup at *current time*. Even though when I go back to the iCloud manage storage nothing has changed, no extra photos, no extra backup has been added.

I rang apple customer support & she ran through some of the steps like signing in & out, resetting the device, trying a different wifi network (all things I've tried) & said it sounds like it should be working

Any idea why my iPhone wont backup, even over wifi? I'm not great with technology but does this behavior indicate anything, like a dodgy file/photo stopping the backups partway? Is there anything I can do to get the backup to actually complete? & any idea why only less than half of my photos are syncing through iCloud even though I have more than enough allowance?!