I will respond with comments in the text of your message.
You write: "I thought that I would start with dic, dict which means to say or to tell."
I'm curious to know the source of your hypothesis of <dict> and <dict> comes from. You are on a good track here, but one key aspect of scientific word investigation is that whenever we present our hypothesis of a morphological structure, we should do so with evidence from a word sum. I see lots of evidence for as a base element with the sense of "speak" or "say, tell" from words like and that can be analyzed like this:
pre + dict + ion → prediction
dict + ion + ary → dictionary
And when I look up the root of both of these words on Etymonline, I find my way to the Latin root dicere. And in these searchers I do find denotations "speak, say, tell". By the way, I like to show the structure of Latin roots by putting parentheses around the Latin suffix. So for this Latin word, I could represent its structure like this 'dic(ere)'.
While this Latin root and its structure does make me wonder if there is an English base <dic>, or perhaps <dice>, off hand, I do not yet have a word in mind with that base - without the <t> we see in <dict>. We can come back to that point later.
In the next section of your post, I'm going to use the angle brackets to identify that these words are not just a part of your sentence -- and that it is the orthography of these words you are studying. When we are presenting a spelling (not just a word) to study, it is extremely helpful to make that clear with those angle brackets. In linguistics, these angle brackets < > indicate that what is inside is orthographic. When writing in Real Spellers, the computer needs you to put the text inside angle brackets in bold. That's the only way the program knows to show what is inside angle brackets. I'm also adding the parentheses to show the Latin structure of the root you write, and I like to use single quotation marks around roots just to signal to the reader that this word is not part of the sentence, but something that is being referred to. Finally, when I write the denotation that we get from a root, I always use double quotation marks. Again, this helps the reader realize that those are not words in the structure of the sentence, but something that is being referred to. I encourage the readers to consider for yourself if these conventions make the meaning of this text easier to follow than when all the text is written in the same way. With that in mind, here is the next part of your excellent question...
"I thought that I would show the two words <dictate> and <indicate> because the stress is different. In looking at these two words and my word list, the words with <dic> and <dict> with the stress on them like <dictate> come from 'dic(ere)' which means to "tell or say" and the ones with <indicate> or <abdicate> that come from 'dic(are)' which is closer to to "show". They both back up into the same root '*diek' which means "show". How do I walk the kids through this? How do we explain going from '*diek' to 'dic(ere)' or 'dic(are)' to and <dic> to <dict> ?
Wow, Shelley, first of all, you are to be congratulated for the path you have already taken. Clearly you have been digging in and researching and have found a great deal of information. Because you've done that and explained the trail of your investigation so clearly, I (and others) can help you come to a clearer understanding of the process you and your students can do. But I want to start by identifying just a couple of key principles of investigating orthography that are essential for any scientific orthographic inquiry that come to mind due to your investigation.
1) Always use word sums to come to any conclusion about morphological structure.
2) Be very carful about the difference between morphology and etymology. It is very helpful to mark that understanding by using the term "base" or "base element" when referring to the current English morpheme (the word "element" in "base element" indicates you are referring to written morphology, not oral.)
3) Do your best as a scientist to never do deeper than your evidence. Never worry about not going "deep enough" -- just go as far as the evidence you can make sense of.
To start to respond to your question, I will just follow the path I would follow with you or any student - or myself if this was my own question.
It seems to me that your starting point is that you noticed the words <dictate> and <indictate> and your hypothesis is that they are related. So the first thing to do is test that hypothesis. I get to share my "4 questions" chart that I just revised last night to act as a guide for our journey...
If I "dictate" something I get the sene that I'm telling someone what to do. If I "indicate" something, I get the sense that I'm pointing it out, or maybe telling them where something is.
So from a simple first pass at thinking about the meaning, there seems a logical connection.
We could either look at the etymological aor morphologiacal relatives next. Since I think it is where you started, lets look at the morphological structure with hypothesized structure with word sums...
dict + ate --> dictate
in + dic + ate --> indicate
The second word sum makes me puase as I notice that it doesn't have the <t>. I also recognize that with that vowel suffix <-ate> the base of that word may be <dice>, so I'll record that second hypothesis for that word structure:
in + dice/ + ate --> indicate
Regardless of what else I find, I see that these two words do not share the same spelling of the base. there is not <dict> in <indicate> not matter what else I find! Cool, so now coud be a good time to look at the etymology. Do they share a history? It's clear from you post that you did this work. I'll paste some of what I found: