Bakuryu,
I think if that's the extent of the bubbles you are seeing after you dilute with mineral spirits, I think you're okay. Mix a little longer and you'll see the number of bubbles decrease, but to be honest I never completely got rid of them, and had no problems. I believe 69Charger mentioned that if you still have a fair amount of bubbles once you've poured it in the tray, you can skim the surface to get rid of the excess, but honestly I never bothered. I found that instead of rolling out the paint from the roller as you would in traditional house painting (using the corregated section of the tray), I just rolled it in the deep section, pulled it out to let the excess drip off, then went right at it. It seemed as thought the more I was able to get on the surface immediately the better, spreading it out quickly so that I didn't have to roll too much to spread it out. Make sense?
More about the bubbles - it was my experience that you WILL still get bubbles when rolling it on with the proper dilution, even if you over-dilute, at least in the initial minutes of application. If the slight puff pops them, fine - as long as you try to get them all gone as quickly as possible - let the paint spread. After a couple of minutes, you can go back over any areas that still have the very tiny bubbles as "69" describes, but do it EVER so gently - just the weight of the roller. If it feels like it's trying to pull up the paint - STOP! You can fix it in sanding. This process of re-rollering to totally eliminate any tiny bubbles is definitely where the "art" comes in. I didn't really "get it" until the fourth coat, then BINGO - it all made sense to where I was able to repeat it consistantly.

It's a little hard to tell from the photos how the finish really is, that's a judgement call you're going to need to make. What makes you think it was too thick? You say you're not seeing any orange peel, so that's good. I'm willing to bet if that's the case that you're not too far off on the dilution. When the paint is completely dry (no more tacky feeling), run your hand over the surface nice and gently. Feel any rough spots? Feel any spots rougher than others? If so, I would take the time now to sand it out and correct the problem before you go on to the next coat, especially if you think it's too thick.Remember, the point of this is to put the paint on thin, so it's not going to cover up any underlaying flaws.

On a last not, I'm really interested to see your progress - KEEP the PHOTOS COMING!!! I have two gallons of the MASSTONE TINT BASE sitting in my garage - untinted as of yet, but I've been contemplating black. It's a bit of a scary thought as black shows EVERYTHING. BTW, when they tinted yours, did they mention any kind of special tint, or did they just use the standard tinting formulas? I asked the Home Depot "paint-guy" and he simply said that he could just punch in "rustoleum" and the tint system would know. I wasn't all convinced he wasn't just making it up as he went, but I guess I have little choice. Did they give you a selection of "rustoleum" colors to choose from, or did they just mix up the color from a swatch?