Wife can't mow, need assistance please.....

Hello, I have a 10-12 year old Exmark laser Z 54" or 60" I honestly can't recall, I am a disabled senior and my Wife has been mowing our 3.5 acres since my injury in 2005, but anyway when she engages the blades the belt comes off every time regardless of how gentle she tries to engage them. We purchased a new belt late last summer but it has progressively gotten worse, to the point the blade belt comes off every single time and she is 66 years old and does not need to push mow this 3-4 acres of lawn and very fast growing old pasture with nothing but trash grass, sage, amoung several other fast growing grasses/weeds. Also the charging system does not work and she has to use NAPA 1500 amp jump starters, it will pull one down and kill the engine before she completes all the mowing so she has two and its requires both, and then they get weaker and weaker from such a deep discharge so we have to purchase a new one every spring and continue to use the strongest of the two from the prior season, that is cheaper than having it repaired although it is very aggravating. As I stated earlier iam a disabled senior and my wife is retired and we survive on very limited monthly incomes and can't afford to take it into the Exmark dealer for repairs, any and all suggestions/recommendations/help is very greatly appreaciated, given the proper troubleshooting and repair instructions our son in law hopefully can make the repairs. Thanks in advance for all that may contribute, not much I can do as I am 98-99% bedridden. Ancienly awaiting your reply.

Thanks

Wife can't mow, need assistance please.....