a) Mono Input:
Your sound card input is probable set to receive a stereo input (see Line 1/2). But a Mic resp. your 528E only delivers a mono signal output, as it is not a stereo device! I also assume, that the cable is not a stereo cable - thus it only provides an input to your Line 1 input of your Delta 66 - but to to LIne 1 AND 2!
Thus it is totally normal as expected, that the signal is mono only - typically the left channel is used.
One option is to double-click on your mixer input channel name to open the configuration dialog and select the 'Mono' option checkbox!
If that is not working (due a possible restriction of your sound card driver) and to still regulate this shortcoming and to duplicate the incoming mono signal to both channels of the input mixer - make a right click on the name of the related mixer input channel and select from its context menu the 'Processing' entry and select 'Standard Mono'.
b) Latency:
Welcome to the world of real-time digital audio processing.
By default Windows uses the WDM/DirectSound resp. WASPAI driver model. This is a very stable, but consumer oriented driver mode, which is NOT a low latency model. I.e. it uses a quite huge internal buffer (often a few hundred milliseconds) to capture and cache your audio signal. And this introduces a big latency until you 'hear' the input signal.
Professional sound card therefore offer another driver model, which is called ASIO and is used in professional equipment.
I guess your Delta 66 also comes with ASIO drivers provided, which you might need to install manually - check your Delta 66 user manual in order to do so.
Once installed go back to you mixer input channel configuration dialog and select ASIO as the driver model.
Important Note: It is recommended to NOT mix the driver models of your sound card!
I.e. you must also switch all other mixer input AND output channel to ASIO to achieve real low latency audio processing!
If your sound card doesn't come with an ASIO driver, you might try a generic ASIO driver:
http://www.asio4all.org/
Else also do a little googeling to get familiar with low latency issues on audio processing.