this may not work so well in MP i understand
This line is going get you some "advice" about MP and what you "must" do to be competitive. To put those inevitable responses in perspective, however, consider the following:
01. The specific form of MP to which they refer is a sub-genre of the game, and a pretty small one at that. Well under 1% of the people who have actually bought one of the Sins games actually choose to play in this environment. However, it tends to dominate the perspectives and comments on this forum.
02. The reason that this type of MP game is so different is that they set the initial conditions to force fast play in a confined and constrained environment. They will claim that this does not change the "balance" of the game (although if you read Incomitatus' detailed comment above about the TEC short, medium and long games it is not hard to see that this is actually not correct as it changes the length of the games and thus the value of different factional technologies being deployed at different times), but it certainly changes the style of play that will be successful. Some, but not all, of what they say can be extrapolated to guide play against an AI opponent.
03. Playing against the AI, either alone or with friends, is fun, as the vast majority of Sins players can readily attest. If you enjoy this type of game, there is no need to subject yourself to the abusive "cage match" environment that I mentioned in 02. above. Some of the players are not very nice, and if you don't do things exactly their way they can be fairly crabby about it. It is worth noting at this point that, with friends, you are already playing a form of MP for which your tactics and suggestions are not at all inappropriate.) Depending on initial random conditions, the games will be very different each time out of the box. If you and your friend/friends then continue the game after the AI players are eliminated, you can experience the challenge of facing a human opponent. In this type of environment, how you manage your respective AI opponents will definitely affect play in the endgame (so feel free to take tips on the short game from the self-proclaimed "experts", but with a grain of salt). In a large universe, however, the game will definitely then last long enough that you will need to re-evaluate a lot of what they say about what to do and what not to do, because their games simply never last long enough for them understand how to prepare for that environment very well.
OK. Enough about MP. Having said that, you made three good observations:
a. If you can get the enemy to focus on your Ankylon, it can indeed take a lot of punishment while you work on taking out his caps and/or support ships. You need to make sure it doesn't run out of antimatter, however, or you lose a lot of its fleet support value and just end up with a flying brick. This is easier to do against the AI than it is against a human player, of course.
b. Twin fortresses, supporting each other with docking booms, fighters and some bombers, can be an effective defensive bastion. They will not last forever if left unsupported, so you should plan to reinforce/screen them with expendable support ships while waiting for your fleet to arrive. When the cavalry arrives, they will then provide invaluable fleet support by supplying your Ankylon and Kols with antimatter (an area in which both are somewhat weak). In the endgame the TEC loyalist should definitely have two at each of his worlds, for this benefit as well as for the extra income that the trade facilities will provide. In a Twin Fortress setup, one auxiliary government, one remote construction, four docking booms, four hangar bays, two trade facilities, four weapons upgrades and six defensive upgrades leaves you...ah...six over the limit, so you obviously have to do some prioritization.
c. The TEC Loyalist economy is indeed the dominant feature of that faction. Not especially well-suited to "cage match" play, but in the long game it really comes into its own. It is what allows them to treat everything in their fleet except the capital ships as expendable. So know when to retreat those caps. Even moderate capital ship losses are acceptable, however, because you can level your new ones up fairly quickly in the next large couple of battles as long as you manage them properly. Because it comes back with all experience levels intact, the Titan is also somewhat expendable, but it can be a lonely 5 1/2 minutes while it's rebuilding.
Above all, despite what some others seem to think, it's just a game and the whole point is to have fun, and there are a lot of ways to do that. Comments from the "pros" notwithstanding. For example, if you choose to play against the AI with friends, you can set up situations where you trade factions and play again under similar conditions, just to compare and contrast things like how long it takes for a game to finish, or for one player to reach a certain number of planets, player stats at hourly intervals, etc. etc.