If you stick with the L, you might want to get the 70-300L first. You can always get some macro extension tubes to use with it, to be able to focus much closer, at least near macro. But, I agree... it's not really long enough for moon shots and not the type lens you're very likely to use for astrophotography. It's also not really long enough for a lot of wildlife, particularly smaller critters and birds.
The last thing you have to worry about with macro photography is bluring down the background. In fact, at higher magnifications you'll be struggling to get enough depth of field, not looking for less. Below was shot with a 90mm lens at f11.... the background is a sidewalk and ugly trash can. As you can see, the background blurs away to nothingness...

IS on a macro lens is kind of silly, IMO. If you get serious about macro, you'll be using a monopod or tripod a lot of the time... Or flash. All of which make IS, which is nowhere near as effective at higher magnifications anyway, less necessary. On the 100mm, IS is most useful when using the lens for non-macro purposes (and you already have a 135L, which you'll probably be using instead for it's faster AF performance.) I would not spend the extra money for IS on the 100mm. I'd put the money saved into a tripod mounting ring for the lens, which is far more practical for macro work. The image quality of the 100L vs the 100/2.8 USM is virtually identical. Both are excellent. The build quality of both is top notch, too. Even though it's not an L, the 100/2.8 USM is identical build to the 180/3.5
L. IMO, the most significant difference between them are that the 100/2.8 USM's lens hood is rather large (and is sold separately)... and the 100L has a somewhat enhanced Focus Limiter feature (three ranges, vs two on the non-L). Because I rarely use my 100 Macro for non-macro purposes, the IS doesn't do much for me, so I won't be upgrading any time soon (unless I win the lottery and just have money to burn).
You really might want to consider an alternative.
For less than the price of the 70-300L ($1400 US)
or little more than the 100L alone.... you could get
both the 70-300 IS USM (non-L, $450 US)
and the 100/2.8 USM ($550 US) plus their lens hoods (unlike the L, sold separately: $44 and $33, respectively, or less if you buy Chinese knock-offs). The tripod ring for the 100/2.8 USM runs about $160, while for the 100L it's about $190, for Canon OEM in both cases. There are Chinese knock-offs for either one, that cost about $50.
Another alternative would be the 70-300 DO IS USM, which is more compact. But it's close to the same price as the 70-300L.
Comparing images from the three 70-300s, you will have a really hard time telling them apart. All three actually have quite good IQ. They also all have fast AF.
The differences are:
Build quality of the 70-300L is definitely the best. Of course, at 3X the price, it had better be.
The 70-300 DO is quite a bit smaller and lighter, unfortunately it's IS isn't as effective as the other two.
The 70-300 IS USM (non-L, non-DO) is slightly longer than the DO, but actually weighs less. It's a little plasticky, Canon mid-grade quality. Although it's got fast, accurate USM focus, it's somewhat a hybrid because it can't do FTM or Full Time Manual override of focus. You have to turn off AF at the switch before manual foucsing the lens (and the focus ring rotates during AF).
But, again, you won't see any significant difference in your images.
Later, if you find you use either or both these lenses a lot and they meet your needs really well, you can upgrade if you wish.
Yes, the 180/3.5L macro does blur down backgrounds strongly. In fact it's got potential for incredibly shallow depth of field, as you can see here...
The 180mm is a considerably more difficult macro lens to work with, than either of the 100mm. The 180mm is more of a dedicated macro lens, less likely to be handy for non-macro purposes. One reason is that it's AF is rather slow, even when the Focus Limiter is used. I rarely use this lens on crop... it's too long. At high macro magnifications, it's going to largely be done on a tripod (well, above image wasn't, but camera and lens were sitting directly on the ground). Due to the shallow DOF this lens renders, it's more likely you'll need to stop it down quite a bit, requiring slower shutter speeds (or higher ISOs or flash, or some combination of these).
The 60mm Macro is an EF-S lens, so won't work on your FF camera, only on your cropper. The same is true of the Tamron 60mm, which I'm trying out right now (it's an interesting lens because it's a full stop faster than nearly all other macro lenses... f2.0).
Yes, the 50/2.5 Compact Macro only goes to 1:2 on it's own. Either with macro extension tubes or it's dedicated 1:1 adapter, it can be boosted. But it's still a fairly short focal length to try to use for general purpose macro.... it can put you too close to skittish subjects... or ones that sting or bite. Or with inanimate subjects, you might have problems casting shadows or bumping them with a lens hood.
In my opinion, 90mm to 105mm is the most versatile "all around" macro focal length. That means in addition to the two Canon 100mm, there are also the Tamron 90mm (two versions, incl. a new one with stabilization and a new, faster AF drive), Tokina 100/2.8, and Sigma 105/2.8 OS.
Personally I really like the Canon 100s because they can optionally be fitted with tripod rings, are internal focusing (don't grow longer when focused closer), and have all the goodies in one package.
I consider 150mm and 180mm macro lenses to be largely "full frame"... a bit long and harder to use on crop.