If I were spending your money and rewriting your lens collection, I'd sell your current lenses except the 50/1.8 (18-135 NON-STM, and 70-300 NON-L) and put that $350-400 towards the overall budget, making it $7200-ish.
Enough people have done exactly what you asked them NOT to do and talked about the CAMERA, so I'll just focus on the lenses (with one exception)...
Here goes my list...
A prime between 45-100mm with a maximum aperture of 2.8 (so 1.8, 1.4 and so on are fine too!)
I can work with the 50mm, but also the 85 and so on, so I just need 1 that is the best.
You mentioned that you use your 50mm/1.8 for portraits and some macro but that it's not ideal for macro - in my opinion, the 50mm field is a situation of picking the least of various evils. The 50/1.2 is expensive and no better than the Canon 50/1.4 at equivalent apertures so you're paying a $1000 premium for a fraction of a stop and being able to say that the bokeh is "dreamy" (and sharpness is non-existent) at f/1.2. That's a lot of coin for crappy bragging rights, IMO. The Sigma 50/1.4 is better than the Canon 50/1.4, but there seem to be some reliability issues among users when it comes to focus accuracy - so you may play the lens lottery which is a P.I.T.A. The 50/1.8 is crap until f/2.8 so... what's the point? Well, you said f/2.8 is fine - so keep it and use it there. My recommendation? 85/1.2 LII. You wanted sharp... this is $2000 worth of SUPER SHARP! If you want to replace your 50/1.8 then the new Zeiss Otus 55mm f/1.4 is a RIDICULOUS lens when it comes to sharpness. You said you didn't mind manual focusing - this is a non-AF lens and is sharper than anything else you'll find, but it's half your budget. Personally, I say stick with the 50/1.8, use it at 2.8, and add the Canon 85/1.2 LII.
A mid-range zoom with a maximum aperture of 2.8 (so 1.8, 1.4 and so on are fine too!)
Everything below 20mm to above 40mm is fine.
Since you're keeping your 50mm/1.8, the Sigma 18-35 f/1.8 constant zoom lens is a REAL option. Really sharp and REALLY fast! If it's turns out not to be then the obvious choice is the Canon 17-55/2.8 as it's sharp, covers a great range, and has IS. The 50mm f/1.8 at 2.8 is roughly equal to the 17-55 at 50mm at f/2.8 in terms of sharpness - but the bokeh is better on the 17-55 and you get IS. Should you go with the 17-55, sell the 50/1.8.
Cost: $800 +/- depending on which lens you purchase. Maybe as low as $700 when you factor in that you can sell the 50/1.8 if you go with the 17-55.
A decent lens for macro between 85 and 100mm. I don’t have a preference for the aperture here.
Either of Canon's 100mm f/2.8 macro lenses are perfect here. If you want weather sealing and/or hybrid IS, go with the L. If not, go with the non-L. Optically, they're very similar.
Cost: $550-$850 depending on the lens chosen
I have the 18-135, but I don’t find that sharp enough. I do like the zoom range though. Is there anything that comes close to the range, but sharper?
Yup! The NEW 18-135 STM. But, you're well covered with the lenses above in terms of sharpness. Either skip the large range zoom OR, buy the NEW 18-135mm STM lens. The glass has been updated and it's a much sharper lens than the old 18-135 lens. As a bonus, it'll work like a CHAMP for video with your 70D. The STM lenses have focusing motors and IS systems that are made specifically for video - they're SILENT
A zoom that goes beyond 250/300mm. If that is achieved by a teleconverter that is fine by me, if that gives me better results.
BEYOND 300 without a teleconverter leaves only a few options. The Canon 100-400 is an obvious option. Tamron just announced a very large lens, the 150-600 that seems to test well. There's also a 70-200 or 70-300 plus 2x teleconverter. Too many options here to list - homework time
Now... one place you're missing some critical range (for some people) and that's the UWA end. In my opinion, when you're using an UWA, you're usually out walking around a LOT. That means, LIGHT WEIGHT is GOOD! The Canon EOS M + 11-22mm IS lens is an obvious choice for this scenario, IMO. The cost is roughly the same as the Canon 10-22 and the lens is BETTER except for the max aperture and 10 vs 11mm.
Cost: $600-650. Another possible use for this money is lighting like an external flash (or 2, or 3), etc.
Total cost of all options above except the telephoto zoom = max of $4600 (before taxes) unless you buy the 55mm Zeiss. It could be $400 less if you go with the Canon 17-55 as opposed to the Sigma 18-35 and the non-L 100mm macro. That leaves you $2600-$3000 for your telephoto solution (because remember, you sold your 18-135 and 70-300 in my scenario). That's enough for the top of the line Canon EF 70-200mm f/2.8L IS II ($2500) and 2x teleconverter!
That's some INCREDIBLE gear!
85mm f/1.2 L II
18-35 f/1.8 OR 17-55 f/2.8 IS
100mm f/2.8 macro (L or not)
EF-S 18-135 STM (for convenience and video - sharpness isn't bad)
Any one of several telephoto zooms + teleconverter
EOS M + 11-22mm IS
With this setup, you're covered with FANTASTIC image quality from FF equivalent of 17-660mm! AND, you have IS as an option the entire way.
That's how I personally would spend the money! Except I'd find a way to add the 35mm f/2 IS ($500-600).