Wody

According to the manual in section 2.4 about the expansion slots, only the x1 slots can be used, the other slots are only for graphic cards. From the pictures, it looks like the x1 slots are not open, so your TP-Link TX401 won't work, since that has a physical x4 connector and doesn't fit.

This happens when there is no internet-connection at the time of booting. And it is related to the Connect plugin. I think it tries to download it from the internet instead of getting it from a stored source.

The ASR-71605 is a RAID controller, not a HBA. This means if you configure the drives, they won't show up since the card is holding them hostage. They can be passed through, but you have to set it to either expose RAW, or HBA mode, and of course you have to make sure the latest firmware build 32118 is installed. I have an 8885 which has a newer build firmware, but the option should be somewhere on the second page of controller options. Currently I don't have the controller in a computer, but if you can't find it say so and I'll install it to give better instructions.

You didn't say how big the drives are, or how many you have, but since data-safety is important and shouldn't be moved around too much, assuming your new drives are bigger than 4TB, replace the parity drive with a new one, rebuild parity, then add or replace one of the data disks, move data from the 1.5GB drive to it, and another if possible, so you have one drive less in use, then move them without the now empty drive to the new (faster) system, make a new config, assign the drives and build parity.

Since it shows no free space used or free, and the many errors in the log, your USB device has failed and needs to be replaced.

1. Yes, although technically you're not supposed to since it might not be a real trial.
2. The license is linked to the USB flash-drive it is currently on, so you can't copy that, but assuming you didn't change the start-menu, it is a case of renaming the config folder, then moving it to flashdrive 2, move the config folder from drive 2 to drive 1, move the licensefile from drive 2 to drive 1, and rename the config folder on drive 2 (so basically switch the config folders, but keep the key on the original flashdrive).
3. Technically Beta and RC versions could have errors that make things not behave like they should, but unraid is very good in keeping things stable, so yes.

Honestly, I'm not sure that is the case. I've tried re-creating the situation, on my X10SL7-F which has the same SAS-chip (although revision 5 instead of 3) with an 8TB HUH728080AL4200 which should be the same type, and it just works.
 
So I started reading your logs some more, found some weird stuff like SAS addresses going 44332211... which turns out to be your SATA drives, so that wasn't anything, but the 'bad' drives do report something, which is their status.
To be specific, after a drive is connected, there is a report 'Sense key 0x2' which comes out of the SCSI specification to indicate something special is happening, which in this case means Not Ready.
Furthermore, it reports ASC (additional sense code) 0x4 which is something with the hardware, and an ASCQ (additional sense code qualifier) of 0x1b which means Logical unit not ready, Sanitize in progress.
 
In other words, the drives seem to be working, but you have to leave them alone for about a day or so to remove old data. If you have the unassigned devices plug in, you may be able to get the drive page, which has a self-test tab, with a self-test history. If you open that, it should say how long an extended self test takes, which should be the same as the sanitize-process it is doing. Leave it alone for that long, and see if it works then. It should report everything okay. I have no idea however, if it will start over santiizing if you change slots, controllers or anything else though, so make sure to keep that the same after a drive is complete to see if unraid recognizes it, and if it doesn't, restart the computer and see if it comes up then.
 
In case this status doesn't mean it is already doing self-sanitize, but it is saying I'm not letting you do anything until you sanitize me, you can use (using sdd as an example):
sg_readcap -l /dev/sdd which will show something about the protection of the drive and the capability (not sure what it all means though)
and to sanitize the drive use
sg_sanitize --type /dev/sdd where type is block, crypto, fail or overwrite. If you do sg_sanitize by itself it will explain some of it.