I am not sure exactly how temperature stable the EM2300 is, but it can do a good coffee with unpressurized baskets and freshly ground fresh beans.
Your questions approximately answered as;
1; Pressurized baskets are designed to give an artifical crema *when using pre-ground coffee, particularly the vacuum packed varieties which are stale before they are packed.
Unpressurized baskets will give better taste on any functional machine when used with freshly ground, as in just before you brew, and freshly roasted beans, as in within 3-4 weeks from roast typically.
2; Regret can only advise you search the forum more for the suitable part numbers and a local supplier.
3; Rocky is a great grinder for your machine that will last a long time, and might just fit into your budget. *Iberital Challenge is highly regarded on this site, a bit cheaper than Rocky, and has good grind quality, only limited by relatively slow adjustment of grind if you ever need to go to plunger grind and back to espresso for example. There may be one or two others listed in the Grinders section that are worth checking out. *The EMO 480/4450 grinders will do the job but unlikely to last as long, (they are more of an appliance than a precision machine).
4; Firstly, ensure the machine is on, with PF installed loosely, to preheat for approx 30mins. *Briefly flush the grouphead to ensure it is clean of any leftover grinds, and that there is fresh water in the brew path, only if the water is hissing and/or steamy do you need longer flush, so you might be better preheating your mug with boiling water from the kettle or jug.
Grind into basket till about half full, vigorously tap your hand against the the PF to help settle the grinds into the basket,
continue grinding till basket is approx full, tap PF vertically onto bench top (you may wish to use a chopping board/mat to protect the bench top) to settle grinds into basket. You will need to experiment with how many times to do this, try once, twice and three times.
After this you can top up the basket with more grinds, level off with suitable straight edge, I use a kitchen knife, (blunt side), tamp firmly with attention to tamping evenly. *If the tamp is a loose fit the *NSEW technique is worth trying, first in the centre, then move tamp as far as it will go towards one side, tamp again, then as far back the other way, tamp again then at 90 deg as far as it will go tamp again, then across to other side and tamp again.
Lock PF into grouphead, and begin the brewing.
Pour should start within approx 8-12 seconds, slowly even drippy at first, then thicker dark stream and will lighten up. *Aim to stop pour around 25 - 30 seconds, using a double basket, at first signs of light tan colour. *Anything around 30 - 40 mls is good enough at this stage.
Change to steam temp, empty PF, you can briefly flush grouphead to dislodge loose grinds now or wait till after steaming.
Blow out steam wand when steam temp achieved, but preferably before the heat cycle has finished, begin steaming with the steam heating on if possible, will give more powerful steaming.
After steaming, pour milk into shot.
Blow down boiler back to brew temp, refill with water, flush grouphead with blank basket in PF (can use any suitable rubber insert)
wiggle PF around with brew water flowing through, this will help reduce buildup of oils in the brew path and shower screen.
By some espresso machine cleaner from coffeparts, or similar, and use this to clean the showerscreen, GH, PF and associated parts about every 2 weeks. *Descaling can be done every 2nd or 3rd month if you dont use filtered water, or about 4-6 monthly if you use filtered water (if it is an aluminum boiler then go for the shorter interval, if Stainless go for the longer interval).
Hope this is of some help.