ZTRs can speed up your mowing job but they are not perfect. They have some shortcomings as do all machines for that matter. If you have steep slopes with something bad at the bottom like a ditch or a cliff....then I highly advise against a ZTR. In worse case scenarios you can lose steering and braking going down a slope of slippery grass. That's something you shouldn't do in the first place though. If the operator gets too agressive you can gouge the yard by turning too quickly. Now for the positive points. They are fun and easy to drive and do a good mowing job. They cut your mowing time in half. They are great in the hands of someone who bothers to learn how to run them correctly. As far as quality is concerned. You get what you pay for. Most residential ZTRs will last about as long as their predecessor lawn tractors did with possibly a little extra time added on due to the newness. (They will get built cheaper and cheaper as the market drives the prices down.) Right now I like most of the big name brands. The Toro should be as good as most other residential machines. (I'd avoid Craftsman at all costs.) If I was in the market for one I'd go with a commercial ZTR like a Scag Tiger Cub or equivalent. These commercial machines will last many years because they are true commercial quality machines that are meant to be used all day every day..

I would think starter fertilizer wold work well when you seed. Then would fertilize again in mid October perhaps again with starter!

I think you have a lot of leeway in timing your seeding in the Seattle area. Since your winters are so mild, you don't need to worry about hard freezes the way most of us who use cool season grasses do. If you like the look of the fescues, they're more shade tolerant than KBG, so you could use them in the shady areas. The creeping red fescue will spread (unlike most fescues). I noticed that your seed mixture contained 60% PR. That's pretty high. PR germinates quickly and can keep other seeds from growing. If I were you, I'd eliminate the PR in future seedings. On the weed issue, if you want to stay organic, a weed hound is probably the best thing you can buy. It should be available at the nearest "big box" store. In my opinion, it's a mistake to consider clover a weed. I consider clover to be beneficial. Black medic (a clover lookalike) is another story, but dutch white clover and strawberry clover are both welcome in my lawn.

You may want to look at Eaglepoint Landcadd. They have "modules" that add on to a cad engine (intellicad)that they provide with the software. Intellicad is an Autocad clone. They used to have a free 30 day demo cd that they would send if requested. Don't be afraid to negotiate pricing. It worked for me a few years back. I have not used the irrigation module.