First off i'd like to say, great guide. Pretty much the same strategy and builds i've been using after some struggling games of testing. For summoner spells i'd definitely suggest Ignite, as you mentioned, and the second one I always get is Exhaust. It works well with his lack of CC.
I bought this champ the first day and didn't really like him at first. He seemed like less of a tank than some other champs, he seemed less of a threat than other DPS champs, and he had no CC's like most other champs. Needless to say this thought process came from being new to the champion and getting roflstomped game after game.
However, this all changed after I started getting used to his play-style some more. It took a number of games to finally understand his purpose and how much he can actually contribute to the team. I've come to the conclusion that he is one of the most well-balanced champs in the game.
I still believe he shouldn't be used as a main tank on a team. If he's built correctly and facing the right enemy make-up then he can become practically unkillable, but, he still lacks the correct initiation of a main tank. He is, however, a fantastic off-tank that can definitely soak up loads of damage to help out the main-tank.
He doesn't even have to build any physical or ability items to become a beast in battle. He can go all out tank-like items (merc treads, frozen mallet, warmog's, etc) and still dish out some heavy damage easily. Don't be afraid to take the hits for your team. If you use your skills correctly you can keep your shield up constantly and live for a VERY long time in a team fight, which in turn means you're doing more damage.
If you have a jungler on your team then go in his direction at the start of the game. If he wants to jungle more than lane then you can hold down your lane 2v1 with ease. Most champions that normally destroy melee champions early (Zilean comes to mind) will be very frustrated with how easily your shield stays fully charged...meaning their spells are doing nothing to you and their harass is failing.
Mordekaiser is really fun (still doesn't beat out Singed, though!!) so if you're having a hard time with him just keep at it. You will learn his playstlye and come to love it in time.