Thunderbird Tekoha Aty

I'm having problems getting my signature to appear in Thunderbird as it does in my soon-to-be former email client. I've attached pics of the signature as it should appear and as it appears when imported to Thunderbird. I can edit the HTML code, but I'm not sure how to correct things like the image not importing when the link is correct and how to get rid of the dotted line border that shows up in Thunderbird when it does not appear in my current email client signature. I attempted to attach my HTML file, but cannot. I can post the code, if that would be beneficial. HELP!

In Windows and other applications when I hit space it moves the cursor or text I have the cursor in front of to the right a certain number of spaces. If I subsequently hit backspace it moves the cursor or text I have the cursor in front of back the same amount of spaces.

This is not how Thunderbird operates, if I tab the cursor or text I have the cursor in front of does move to the right 2 spaces, but when I hit backspace the cursor or text I have the cursor in front of moves back a single space at a time.

1) Is there a setting that I can change to have backspace move the cursor or text I have the cursor in front of the same distance back as the initial "tab" moved it to the right?

2) Can I adjust the number of space "tab" jumps from 2 to say, 4?

Thanks

When using Thunderbird 140 I am able to setup the background color of the message pane for individual messages. However when the messages are threaded, the message pane shows a preview of all of the threaded messages together in the message pane with a different background color than individual messages.