First for your specific questions:
At a high level a D1 programs play 56 games plus any playoff games, at the D3 level it is 40 plus playoff games. D1 travel is more demanding usually a Fri/Sat/Sunday game with a mid week game thrown in. D3, they try to compress it into two days if a facility has lights with one day a double header. Top programs are also playing a mid week game For Northern Eastern D3 programs their 40 game schedule gets crammed into two months sometimes and some teams are playing 5 games a week, but they don't play much in Feb, For specifics you really need to look at the programs who are recruiting you.
Over all the travel will be much easier in a D3 program, due to fewer games.
Top D3 programs will eventually get to the 50 something game number if they are consistently in their conference tournament as well as Regionals and CWS games.
My son plays for a top D3 and they usually end up with around 50 games played, since they pretty much always go to Regionals.
Practice and Fall
I am not sure of the exact differences between coaches contact hours for D1 vs D3 to get the exact technical number you can look it up at the NCAA in their coaching manual, I believe it is 20 hours per week for D1, but the reality is that teams have "captain" practices so you will be practicing more than 40 hours a week. For top D3 programs probably a little less then this, but not much. In a D3 program it is not unusual to miss part of, or sometimes a whole practice due to a class conflict. Some D1 programs allow this, but not many, again very program dependent.
Playing for a winning program vs a loosing program. My son did not realize this when he made his decision, but some of the D1 programs who were recruiting him were not in the top half of their league, conversely the program he plays for wins most of their games. They are always in their conference tournament and Regionals so they play a lot of important close games. Playing for a lower level winning program vs a higher level mediocre one is something to think about.
Very dependent on the schools you are considering, Academic money is usually for 4 years, athletic is usually year to year, and is typically performance dependent.
As Soylent said, it is important to select a school that fits your profile and interest, independent of baseball first and then figure in the baseball equation. The difficulty and time demands of your major will also play a part of your decision.
Good luck it is a good problem to have.