My suggestion would be to guess on say, one or two questions that you know are really tough and which will take you a long time to do. If you guess early on, it will reduce the time pressure and then you can focus on the remaining questions.
Also on the Multi Source Reasoning, don't worry too much if the first question takes too long. From what I've learnt on the
MGMAT IR workshop, these have slightly more weight. Additionally these are like RC questions, so spending time up front to understand the question will increase your chances of get them right.
If I were you, I would evaluate what question types I'm weak in and accordingly formulate my strategy (in regards to which questions I'm willing to 'let go').
I also know how you feel; I only recently started my IR prep and I quickly found how poorly I was performing. But like I said, focus on what you're good at for instance, it seems like your verbal is pretty good. You can definitely count on getting a few of those types. All in all, keep your head high, stay positive and remember that the IR is just the appetizer and the main course is still the Q/V sections.