Why? In my opinion SMD is not only easier to handle during the design phase but is even faster to solder. At least as long as you choose smd parts with large enough pitch to hand solder. At the beginning i would stick with gullwing parts so SOIC and QFP.
Soldering THT means you need to place the part, turn over the pcb and hope nothing falls out, solder, cut leads repeat.
SMD only requires you to place the part and start soldering. Only possible downside is that smd parts are typically smaller and you therefore need small tweezers
As long as you stick with large pitch components (1.27mm) and resistors/capacitors >= 0805 you do not really need magnification nor do you need a special solder iron. A decent temperature regulated iron with chissel tip should do just fine. It is of course easier with good tools. (I would say this is the same requirement for THT as well)
Why? This really seems excessive. 0.25mm is easily manufactured even at home.
This is the worst suggestion you made so far! Dealing with nasty chemicals is simply no longer worth it with cheap board houses available. With a professionally made pcb house you get two layer boards by default, plate through holes (useful for vias) and most importantly solder mask.
The only reason to use self made boards is if one has an interest in this process. (The considerations needed for home made boards are so far removed from a professionally produced one that i do not even see an educational value here. All you learn is that chemicals are nasty, that it is a lot of work, expensive and the result is shitty without investing a considerable amount of time into fine tuning the process and investing in good tooling.)
I learned the oposite to be important. Without deadline people do not work efficiently. They start to obsess about unimportant stuff and never finish a project.
I would start with two layer boards! It is much easier to work with two layer than single layer. If one has the money 4 layer is the way to go. (a continues ground plane makes live much much easier. Not only for designing the board but the result will behave better with regards to EMC)
Assembly houses really are only useful if one makes something that should be sold. Otherwise it just is not worth it. (unless you have money to burn)