1

You will probably make it but I would recommend having a backup plan. The biggest variable is immigration line, which may go from 0 to over an hour wait. When there are many arrivals just before yours, there will also be a line at customs, where they x-ray everybody's luggage and everyone has to press the red/green button (red=additional luggage check).
If you arrive at T2, you will then have to go to T1 to check in with Interjet, easiest with Aertotren. There may be line at Interjet counter but they may give you priority due to tight connection. Security is usually not a problem.
If you get there too late they will probably try to put you on a later flight, if there is one. If there is not one, you may wait till next day, or head out to San Lázaro/TAPO, buy a ticket and bus it to Oaxaca (~6hrs, frequent evening departures).

2

You may not necessarily have to change terminals. Which airline are you flying in on? If you have separate tickets then you will have to check-in from scratch at the Interjet desk and their policies are that this must be done 2 hours before departure. So they have every right to sell your ticket to another passenger before you even land! So regardless of how quickly you can get through immigration etc. you could be well and truly stuffed. If you are flying in on any other airline (non-Interjet) I suggest reconsidering your plans.

3

This summer I remember meeting some tourists at the Mexico City airport who were flying to Oaxaca that morning, we were on the connecting train from terminal 1 to terminal 2, so there must be some flights from there to Oaxaca.

4

I don't go through MEX anymore as there is a direct flight from Houston. In the past I have made it multiple times with only an hour. Would you have to go to Immigration in MEX or now that OAX has it, do you go there? If that's the case you should have plenty of time.

5

It really depends on when Interjet closes their check-in for their flight. That's the real time you need to make. Sounds too close to me. Call Interjet and see what they say

6

Agree with Yose01 most likekly you will be OK.

7

Just flew in from San Antonio to Oaxaca on AeroMexico with a change of planes in DF, and had to do immigration in DF.

8

Arriving MEX from LAX at 4:00 in the afternoon

A little (relevant) nuance: scheduled to arrive MEX from LAX at 4:00 in the afternoon. Nobody can guarantee your flight won't be delayed.

9

is your flight to oaxaca with aeromexico? last year i had a bad experience where they oversold the flight and i ended up having to stay in mexico city for a night. the good part was that i got a free ticket out of it and was able to go BACK to oaxaca this year. if you are traveling with the same airline all the way from lax to oaxaca then i agree that you will be fine. if you're switching airlines, then i would try to check in online for the mexico city - oaxaca part of the flight.