Power Connect 5548 LAG LCAP Settings

Hi Please forgive me but im quite new to managed switches but eager to learn and to configure my network in an optimal way.

Basically we currently have A watchguard Firebox (firewall) with VLAN rules plugged into one of  5 Nortel Switches in a stack and have aquired 2 New Dell 5548's setup with HDMI in a stack which I want to connect to the nortel stack in a redundant manner, after some reasearch it seems that creating a LAG using LACP is the way to proceed here. The Nortel stack, Consists of 1x 4548GT-PWR and 4x 4550T-PWR.

Now Ive done a lot of searching and Ive configured the dell switches ready for the connection but i want to make sure I have everything on the dell side setup correctly before i plug into the Nortel switches which I should have some help doing from our phone system support.

So in order to Help clarify what it is that I need. The network we currently run has around 8 VLANS some listed below:

VLAN 1, C-LAN, Computer LAN for the Client Machines
VLAN 50, S-LAN, Servers etc
VLAN 120, T-LAN, Telephone Lan, Nortel VOIP System*
VLAN 60, V-LAN, Phone servers and recording etc*

*we wont have any VOIP phones on these switches as the switches are not POE but may have some phone system componants in the future, However I will try to keep all phone system traffic on the Nortel Switches as they will have all the relevant settings for that.
Note no ISCSI Traffic (we will have seperate switches for this and dell are setting these up)

I need the new Dell switches to connect to the Nortel Switches in a redundant manner so my idea is to have 4 links from the dell switches to the nortel switches using a LAG (no point using the SPF ports as the nortel ones are gigabit speed), on the dell side the ports will be gi1/0/1, gi1/0/2, gi2/0/1, gi2/0/2. Once the LAG is setup I need to be able to configure the Dell switches other ports to specific VLANS so the majority of the ports on the switchs will be used for C-LAN (VLAN1) Access, some of the ports with be S-LAN (VLAN 50) access which will mostly be used for hyper-V hosts (hosting domain controllers and so on)

Hopefully that all makes sense and you can see the reasoning behind it all.

So on the dell switches Using the GUI Web interface (im not so confident with CLI's), I have setup the VLANS, C-LAN Example:

and Have set up the LAG as follows: LAG1

Lag1 Members:

Example port perameters for a port in the LAG

ports 1 and 2 on both switches unavailable to assign to a VLAN as i would expect

This is the main settings screen that im unsure about, I have setup the LAG as a Trunk which from searching I think is correct, but the VLAN List and Native VLAN setting, Im not sure what I should be putting Currently All VLANS are listed in VLAN List followed by (I) except for VLAN1

Finally here is an example port setting for port gi1/0/3 a port not in the trunk, I want this port to be default VLAN 50 to pick up DHCP for this LAN and be able to communicate across the trunk. what im unsure of is do I need this port to be tagged and should all ports be tagged on both switches. how would the switches handle untagged traffic?

Ive done a lot of googling, and I think I know how its supposed to work, and Ive read the manuel for these switches which helps a little but it doesnt explain some of the questions above and I want to make sure its right before i plug anything in and take the network down lol. Should I be enabling Storm control Just incase? or should theis not be neccasary.

Until im sure the link is working i wont be plugging any devices in other than my management workstation to access the GUI, however I would like to be able to test everythign is working and not causing any extra chatter on the network, is there a way to test fo this, or should i just test each port in the lag on its own to see if the lag and communication to the nortel switches stay up, for instance pinging a sever from my managment workstation?

sorry for all the questions. I hope someone can help

Thanks