You can't renew a DTV. When the five years is up, you have to start from scratch again. DTV is classed as a tourist visa. Tourists don't need a 5-year licence on a 180-day stamp
Not if you use the 65k transfer method. It's only 400k which is frozen, and to meet extension criteria you must have this minimum in your account throughout the year anyway. I can't see the problem
Whether you have built a 5-bedroom mansion on the river in Bangkok, or you rent a studio squat in the Khlong Toei slum makes zero difference to visas. You can get a "married to a Thai" visa which you will need to extend each year, and each year you have to prove to immigration that you're still married. Another option is a "retirement" visa, which is dependant on finances (either savings or income). Probably the best hassle free visa is the Long Term Resident Visa for Wealthy Pensioners, which is ten years multiple entry, and costs only 50,000 baht. It's the most hassle-free if you meet the criteria