On #1, it does sound fuel related and probably the first thing would be to look at the carb and potentially do a re-build... if any ethenol fuel was left in there and the boat sat for a period of time, it could be gunked up in some places, perhaps clogging a jet. If it ran fine the first time you test drove it and then didnt.... point to possible trash in the fuel clogging something. However, it also points toward replacing any fuel filters you have in-line since it sounds like as you bump up the rpm, it starves for fuel and stalls so its not delivering the fuel the motor needs to run at the higher rpm's. I would also suggest replacing the fuel lines since if they are original they could be badly degraded on the inside, some of those old fuel lines will collapse as you increase rpm and not allow fuel flow.
Doing a tune up is also in the cards since it could be related and is something you want to do regardless unless you know it was done recently....new plugs, wires and replace the distributor cap. Distributor cap gets corrosion on it and is a "wear item" and meant to be replaced every so often. That can cause all kinds of strange issues to happen.
Don't forget replacing/servicing the impeller as that is really important to a healthy engine...at very least pull it and check the condition. (Pro tip)....use something like dawn dish soap rubbed on the impeller to make re-install super easy. You basically turn the impeller as you are pushing it back into the housing and with the soap lube, it goes much easier. It also helps impeller to stay in good condition since it will run dry a few seconds before the water gets too it when you re-start.
#2 sounds like your steering cable is bad, that happens. You probably also have a grease zerk for your rudder box, its typically at the very back of the boat where the rudder box comes thru the bottom of the boat. That may help some....but likely your cable is the main culprit. Youtube has videos on how to replace, its not too hard... just be sure to use your existing steering cable to pull the new cable thru the hard to reach areas or you could spend a lot of time trying to fish the new cable thru the right places. Also check your rudder visually under the boat and make sure there is no obvious damage that is making the steering real hard....at that age it may be worth putting new packing in the rudder box at some point. Any maintenance you do is gonna make your overall experience better as well as keep the boat in top shape.
Good luck and congrats on the boat. Good looking boat and the best family time ever