these days, can't even ask any questions and not be judged !!
Returning to your original 3 questions, I'd answer as follows.
1) It's possible the engineer is either missing something or has caused the fault. Then again he may not, how can anyone tell from behind a PC screen?
2) Only you can answer whether or not to get someone else involved. If 1st chap won't reply you've little option.
3) How do expect anyone to diagnose without a visit? Contrary to what some people believe, we don't just go round resetting on/off switches for a living and there is actually a skill to what we do. Diagnosing remotely requires a competent person at both ends of the communication.
The only area I'll judge you on is the bit where you say you can't afford etc etc. At over 60, you should be wise enough to expect the unexpected. Failing to plan your life's finances accordingly means having to be prepared to go without.
Harsh but true!