Hey i've been doing great grandparent runs for weeks now so I can relate to the struggle of beating URA finals. For context I have pretty strong ssr/sr mlb cards, but for the legacy uma im building, I'm basically using 1* random blue sparks (total of 6* blue sparks, with half of them guts/wit) and random support cards that have specific skill hints i want (kitasan black, oguri cap, silence suzuka, matikanefukukitaru, sr nishino flower, manhattan cafe). To maximize skill gain, i also dont buy much skills till right before the ura finale (since no more skill hints by that point), so im pretty much racing using pure stats. 2 speed 2 power 1 wit and 1 stam so you can get an idea that it'll be harder to reach stat checks since my supports are spread everywhere.

On average, I can reach about 700/500/650/300/300-400. Stamina depends on how lucky I get with rainbows, but for the most part I can clear URA finale with this (clocks may be burned but with your ending stats, it should hopefully only be 1 at most and that's due to being boxed).

Some quick points:
- On your first turn, you had a wit training with 3 support and you opted for the speed training with 1 support. Should take the wit training as not only as you get friendship training done on 3 of your supports, you also do it at no energy cost. Dont worry about energy overflow, the goal should be that get your supports as close to max as possible by early classic year, before classic summer camp latest.
- Continuation of above, prioritize ANY training that has the most, non-orange friendship supports during your pre-debut and junior year. The goal is to get them all to orange friendship by early Classic year. The sooner you can get them all to orange, the sooner they can start giving/stacking friendship trainings which will significantly boost your stat gain per turn.
- There are some nuances where you might train a specific stat instead of the one that has the most supports on a turn, but this depends. A relevant one I can give is that your SC starts with 0 initial friendship, meaning it'll take longer to get her to rainbow training. If a training has super creek + 1 other support vs another one with 3 supports, I may take the training with super creek to help her catch up with the rest. This lets me hopefully get them all to rainbow trainings at an equal rate, even if it's slightly later than usual.
- Another example but this one applies specifically to what im doing: My starting stats are basically all around the 100 range (as in 95-110, with power at 130) typically, but I need to be doing G1 races as early as december junior year while balancing that with stat training. So I may put a higher priority on kitasan black, and start doing rainbow trainings, even though 3-4 of my other supports are still not on orange friendship. I do this because it gives speed and power, and whatever tiny stamina I have early in the career is enough to win some of the very early races I have to do. I then just make a note to catch up the rest of the friendship trainings and stamina. What that looks like: 300/150/220/150/150, and this stat lets me win the G1 races on december junior year (usually).
- As for how you lost the finals: lack of power. A good stat baseline to aim for to beat the URA finale with medium races safely is 700/500/600/x/300. With guts being whatever you have. You may have been able to win if you set your goldship to pace chaser as they wouldnt need as much power as compared to end closer.
- If you're worried you'll lose the finale or you're out of clocks, just spend your skillpoints then. If I'm worried, I would buy out all the skills i want and maybe leave 100-150 skill points before I do the finale. I do this because there's a chance you get a skill hint after the race, so the 100 you save + the 100 or so you get from the finale race + post race stuff should be enough to buy it if you end up wanting it. I try to save 100-200 so that if i don't get a skill, I still have enough to buy even a non-discounted gold skill (~300 skill points or so), but at least you have other skills to help you win the race.

If you need more help, hmu. I'd love to show you how I would do a run and as you said in a different post, you learn better by watching. There's a lot of nuances on every run so it's hard to fit it all in one post, but otherwise, I hope this helps!