MWaldhauer

If your router supports DynDNS you can use that

It most definitely is not! RAID 5 and 6 are smarter because they don't use up so much disk space and nowadays controllers are OK at handling it, writing to the array is still cumbersome. Software raid is horrible and pose a lot of problems unless we are talking specifik storage solutions like FreeNAS or Unraid Most raid controllers have drivers so you can install windows.

Just a quick note... if you split an ethernet cable in two you would only get 10Mbit speed and a Gigabit switch will do 100Mbit just fine

It's called Kiosk systems... there are a lot of them out there

What we normally do for customers is go out and make a site survey with some special equipment to get a complete overview on how to deal with problems like these and then give a recommendation on a good networking solution for you. But as a start i can recommend that you get a Unifi UAP-AC-PRO access point and put in your shop. This will do the job perfectly in most cases. If it needs to cover a large space, more than one is properbly required.

No problems...

Check your router configuration. Sometimes a setting is configured to not allow traffic between WiFi and LAN

Let's just get something straight here... CAT is by no means anything to consider on the hardware aspect. It is simply a cable standard. Cabels created with CAT5e is minimum requirement for Gigabit ethernet up to 100m. The only exception you have to running higher than CAT5e is if you have a lot of interference in your environment (or if you are capable at running higher that 1Gbps). A good example for a simple switch to expand your network is this: https://www.amazon.com/Cisco-SG100-16-16-Port-Gigabit-SG100-16-NA/dp/B008B8CVTQ

Share permissions are only set for the share it self, not the folder. e.g. as soon as a user is authenticated NTFS permissions takes over. Normally Shares are simply shared with Everyone Full permissions and then usage and access is then controlled by NTFS permissions.

SFP+ is basically just a plug. You need to add a gbic card into them. there are "cables" with gbics in them, but it must be supported by the device.

Go Unifi all the way for ease of configuration and sweet functionality. This is my home setup: I run my controller as a docker on my Unraid server. All you do is define your networks and wireless networks and you are good to go If you run multiple AccessPoints on the system you get awesome roaming and stuff I run a USG, USW with PoE and an UAP-AC-PRO. The USG max out at around 500Mbps so go for the PRO if you need more than that.

Try disabling Windows 10 P2P updates, traffic probably overloads the switch CPU if its an old 100Mbps switch

Does it work if you set an IP address manually and define the gateway?

b is bits and B is Bytes What type of connection are you running ?

Dont use PPTP VPN... it is insecure. PPTP Uses a protocol called GRE for communication witch doesn't have ports like TCP does... 1723 is only for initial connection. Furthermore to my knowledge it is not possible to change the PPTP port.